I am facing issues on my Andoid tablet (Edge and Chrome browser). No issues on Windows desktop. I have noticed that when I use saved username/password, the chances of login error are higher, even though credentials are stored correctly in the browser.

It seems more like a application firewall, like Cloudflare's WAF product. I have the problem constantly while on VPN and frequently otherwise. I typically need to use a residential proxy or a mobile hotspot to sign in.

Incidentally, FT uses cloudflare, and it blocks me unless I use a residential proxy. Sucks.

I had an odd issue today. I don't know if this is a one off. Or, if it is worthy of it's own thread.

I had no problem signing in. When I tried to purchase a ticket, the site kept returning to the purchase page. And that page showed no error messages. So I tried a few more times. Then surrendered and called. The ticketing agent had the same problem. So she called her help desk. 42 minutes on hold waiting for the solution. It turns out for some reason my primary card (which is a regular AX Platinum) had suddenly stopped auto populating. It still showed the same as in the past from my side and her side. After she manually re-entered the number, the purchase went through. BUT, after I hung up, I was looking around my profile. The site had also deleted my KTN. Just a heads up in case anyone else has a similar issue. My information was fine when I traveled yesterday (as an additional fyi).

This whole website and its functionality has a discernible Made in China feel to it

I'm pretty certain this time around this problems related to those who have upgraded their MAC OS to Sonoma 14.x.x. I ave not been able to log in on my computer since early December. Safari worked fine for me until then. No browser on my MAC works. I get the "your credentials are not found..." message instantly. I can log in on the app and using my friends MAC that is not yet on 14.x.x. I also spent hours with Apple Support trying so many things, sage mode, private pbrowsing, new user account, even full reinstall of the OS. I also stopped by the apple stopped by the Apple Store and used one of their computers, all of which are updated to the latest OS, and I get the same error. Lastly, I have a tech friend of my to try logging in on his computer, ore upgrading the OS, which he was able to. He then upgrade to Sonoma and then was no longer able to login. Delta IT needs to fix/update their website code. Don't waste your time with anything on your computer, as the issues lies with DL's website and its compatibly with Apple's most recent OS.

Interesting - that could be it.

But you said "No browser on my MAC works". I'm on Sonoma and Chrome works just fine for me to log in. So I think this is limited to Safari.

Interesting, as I have downloaded Chrome again today and am now able to log in without issue. This was not the case when I downloaded it in early December. Thanks!

Chrome does update all the time - maybe some older version had the same issue that Safari with Sonoma now has. Delta! Here's a clue!

Listen, I'm a nobody, but I know this stuff really well.
As I've found MANY times (most recently with Hertz but also Delta), there are tons of technologies that travel providers (and others) use, of which (if blocked/stopped) any can cause a site login problem.
Firewalls (less likely now), VPN's, CASB, SSPM, cookie blockers, and all sorts of stuff can screw it up. As can anti-DDoS tech from Imperva (Incapsula) (or Cloudflare or Akamai) which I found at Hertz, but it fell on deaf ears.
And yes it can vary with Edge vs. Chrome vs. Safari, even though they use the same Chromium renderer. Updates can cause a mess (i.e. Chrome 102 > 103, or 120 > 121) for no particular reason. Sometimes you can prevent "refresh" and core updates, other times you can't.

My findings on Delta today are that (1) the preference controller is throwing a 404/not found, (2) siteintercept.qualtrics.com (and many many child sites) is (are) often blocked, (3) bat.bing.com is flagged as malicious, (4) advertising sites - now used for other purposes - are stopped by tracking blockers (go-mpulse.net, secure.adnxs.com, quantummetric.com, flashtalking.com and doubleclick.net now Google)

But who the hell at Delta cares? 800-SKYMILES goes to central reservations, which is like "duh... let me connect you with IT/tech..."

Can't log in to the desktop website this morning. Keeps saying it can't locate an account with the information provided. App is working fine.
Tried multiple browsers now and in private mode etc. If I intentionally put in the wrong password, I get a different error that the login credentials are incorrect. So something is broken on DL side again.

I Signed up today and everything was fine. When my session expired and tried to sign back in, it didnt recognized it. I tried the following and failed

-Turned off Mozilla VPN
-Add Delta.com to Internet Options
-Reboot
-Try in Firefox's Private Browser
-Remove AdBlockPlus
-Cleared Firefox's Cookies

What did work was popping a Virtual Machine and logging in on Edge on the VM. Seems to be a problem with my computer.

Best Buy is also encountering a similar issue where i tried to make a purchase and when i put my information, it gives me "network error"

Working for me now in Safari.

As of today Safari is now working for me again…I don’t know when this happened as I hadn’t tried to login for awhile! I read “josephstern’s” post above, went to login on Safari…et voilà!

I just posted a response on a similar post, but, I am currently unable to sign in from my Mac/Safari/Monterey, also unable to sign in from my Mac using Firefox. I can sign in to the Delta App using my iphone

Unable to login on Safari, Chrome, Firefox, TOR, or Duck Duck Go.

Steps I tried:
- renewed my DHCP lease
- Connected to my hotspot instead of wifi
- Restarted my Mac
- Cleared all browser data, including cache and cookies

Nothing has worked.

Can still login on my phone, but hate using my phone to make changes.
I called Delta and they basically said they've never heard of this happening and have no idea what to do. She told me to take my laptop to geek squad.