So, I recently discovered that three of my flags in the last week have been declined, and, as a result, I am under a flag ban. I cannot flag posts for any reason, and, when I attempt to do so, I am redirected to a list of declined flags over the past week. However, the banner informing me of the ban fails to list an end time or date for the ban. How long do flag bans last?
Flaggers with a recent (past 7 days) flagging history consisting of at least 10 handled flags where >= 10% of flags were declined will see [a warning displaying the message "Attention: some of your recent flags have been declined - please review them before flagging this post!"]
Once you get past 25% the message instead reads:
Too many of your recent flags have been declined - please review them instead of flagging this post!
This is where you are banned from flagging stuff.
Later it says (emphasis added):
Depending on when and how those declined flags were cast, this block could last for as little as a day, and won't ever be longer than a week.
According to the answer to this Meta meta post not more than a week. That may now be out of date as there are several other posts concerning extensions to bans.