At least once every 10 days or so, I will receive the font box asking me to find replacement fonts as it would do when a font is not installed. All fonts are installed though. I have to shut down figma and reopen. Once I do, I no longer get the message. It is an easy enough fix to reopen, but not sure why it is happening.
Sorry to hear this is happening! Is this by any chance a file you share across your team?
We find that strange font issues are nearly always caused by the use of conflicting font files across a team. This means that editors on a file are using different versions of a font (which has the same name) with slightly different sizing or spacing which then affects the file each time it is opened by someone with a different version.
If so, our Help Center has more information about resolving this kind of issue: Manage conflicting fonts