It's not clear why the "Zone E" desks would be closing at 6am (or whatever time it was), which would be peak departures time and when you would instead expect extra desks to be opening; it's also very surprising that they would give you the luggage labels there (if that's what you mean by "stickers for the suitcase") but NOT accept the luggage. Are you sure you weren't sent to Zone F to sort out some issue such as paying an overweight fee, drop off of oversize luggage, or something else?

When you met the unhelpful staff member at Zone F (where, again, it's not clear why you would have to ask for help to ""move the belt" to drop your bag - why didn't you go to a manned drop-off desk??) you should have been in possession of a boarding pass showing a timeline for your flight, containing a "Bag Drop" time and an "Arrive at gate" time. Regardless of what this unhelpful staff member told you, you clearly were confused by his conflicting, unexpected, and crazy instructions. Why didn't you find another staff member? The time to act was then; you should have known that you were rapidly running out of time. I know of no airport anywhere that only accepts luggage starting from 30 minutes before. Why didn't you seek a second opinion?

As you have travelled with Ryanair before, you should presumably have known you should be at the gate area, i.e. airside and past security, at 30 minutes before departure, rather than remaining landside waiting to check your bag. Are you sure that there was not some miscommunication where the phrase "too early" and "too late" became mixed up? Alarm bells should have been ringing for you when you see that you are getting so close to your departure time - written in black and white on the boarding pass in your hand - and the person you talk to says "too early". (Just to make sure - did you turn up on the wrong date?)