Have you tried doing a full file check on the patcher. And also verify your time is correct on your computer. I have had no issues with logging in but seem to remember having the issue a couple of years ago and that was what resolved it for me.
Do you use a VPN? I use a VPN for Netflix and when I forget to disconnect I will sometimes get those messages.
I am having this exact issue right now, but it takes me about 10 times to log in. I didn't play for a couple of months, then I updated my clients. And I can't hardly ever log in.
I installed UO on my sons computer and I can login everytime on his computer.
uninstalled UO and deleted folder, and re-installed and I still can't login very often.
No I don't use a VPN on this computer,
I was able to fix this by using a VPN. Having a VPN active allowed me to connect every time. Nowadays though, i can connect without using the VPN.
So I found out logging on my son's computer was a fluke. It would take 10 times on his as well.
I used a VPN for a couple of weeks to play UO. But I figured it out it was my router. Plex stopped working outside my network as well and while debugging it I learned about a feature called UPnP I found it in the menu and it had plex going to the wrong internal IP address. So I toggled the feature off and on, and poof Plex started working outside my network.
Then I'm like humm wondering if UO works without a VPN. And yep it works fine now. So I don't know if everyone's issue is UPnP but I bet it's a router issue anyway.
I don't use VPN. What am I missing? I thought it is for people downloading movies or music illegally.