I couldn't find anyone else with this issue online and need to know how to fix this.
Looks as if you may have removed a font that is included with Windows for apps to show menus. Put back any and all fonts you recently removed.
That's odd, I haven't removed any fonts on this computer before.
unfortunately this did not work
Do you have other applications running while Illustrator is in use? I ask this because I have had a couple of different type families act up on me when I have CorelDRAW and Adobe Illustrator running at the same time. If CorelDRAW is open certain weights of a couple of my type families disappear. But when CorelDRAW is closed they're all available for use. CorelDRAW on its own has issues. I have two versions of it running because one of the same type families in question only works correctly in CDR 2018 while all the bold upright weights of it disappear in CDR 2020; they all show up as italic.
I had contacted the designer of one of these type super families. He wasn't aware of this glitch. But he told me that Microsoft Windows is very primitive in how it handles font naming tables. The short of it is Windows only thinks there are four weights of any typeface (regular, italic, bold and bold-italic). When you have type families that expand way beyond that in terms of font weights and widths some tweaks are required.
Do you have the Verdana (4 faces) and the Tahoma (2 faces) properly installed on your machine? These are the fonts Adobe uses in its menu panels.
How do I tell?
I have Verdana (4 faces) and the Tahoma (2 faces) on my machine but how do I know if they are properly installed?
If those fonts are in the Windows\Fonts folder they should already be properly installed.
So clearly that wasn't the issue. This is so frustrating.
How many "Segoe UI" fonts do you see in the Windows font folder? (Not just "Segoe" but "Segoe UI") I see 12.
12 for me as well.