Same here. Same behaviour in the 'options' window since the recent manteinance. I even have reset my API Key to no avail. The API Key itself works fine with all the endpoints I've tried so far, including the GetUserSummary endpoint that Launchbox log shows as the one being used to check the credentials. Also, achievements are working fine in each emulator I've tested so far.
The command: curl -s "https://retroachievements.org/API/API_GetUserSummary.php?u=[redacted]&y=[redacted]" with my login and key works fine:
Queries to this endpoint with different 'g' and 'a' parameters to the default seem to work fine as well.
The same command with a wrong Login or Key gives:
It looks like everything works just fine. Tested several other endpoints and they seem to work.
Launchbox log gives:
Which is strange. Might be the case of Launchbox User-Agent query being rejected but I cannot check since I don't know which User-Agent is actually using.
Perhaps you could enable debug logs and check the same exception occurs and results in the same 451 error?
TL-DR: Launchbox shows the key as invalid in the options window even with a correct, functional and tested key. This error happens since the last RA manteinance.
Achievements work fine for me in emulators for the time being, the only place they just don't work is the "achievements profile" of the Launchbox UI, where you can check the points, games recently played and such. Since this element is not working, is not showing on the top bar where retroachievemnts points are usually shown. Also "Failed to grab achievement information!" message in the "View achievements profile..." option in the menu. This worked fine prior the recent RA servers maintenance
Thanks in advance