Any more tips other than these to process payment from US credit card for a LATAM Brazil flight:

1. Cleared cookies
2. Tried different browsers and computers
3. Tried app
4. Tried incognito
5. Tried VPN to Brasil
6. Tried different countries sites including BR, CL, AU, US
7. Tried paying over the phone using multiple different credit cards and none of them worked and the rep said to go to the airport to buy

No attempts seen by the credit card issuers.

Is the best way to go via OTA?