when opening an Indesign file I get message for missing plugin. I can still continue and work on file but then need to save it again. Also can not create a book in Indesign
It looks like those are InMath plugins.
This thread may shed some light:
If you aren't using math in the document, try saving the file as IDML, closing and reopening. If that works, save the file as an INDD file again. If you are, you will want to track down the plug-ins: movemen - MathTools READER.