Regarding error in fonts

When I open any scores or projects, the error about missing font style is always popping up. I’ve checked my font book, and it shows that Petaluma font is installed. So why do I get the error message about missing italic style for Petaluma font?

Petaluma Regular is the only variant of Petaluma that exists.
The missing font dialog tells that you don’t have Petaluma Italic. You don’t - it’s entirely correct.

See this thread, for instance, and read down at least a little: