InDesign issues importing AI file "Failed to open PDF file" error

[defaultltgnuod6zreg]

I just updated ALL Adobe Creative Cloud apps a few weeks ago.  I used InDesign to make an interactive brochure last week- no issues whatsoever.  All pages were "placed" directly from an existing multipage AI file and it worked perfectly.  

Today I tried to create another almost duplicate brochure from last one using an almost identical AI file from last week and I kept getting the attached error, even if the file wasn't a PDF but an AI file.  All settings are the same as the last file I was able to create successfully.  I even tried saving the AI file as a PDF but still got the same error.  Any insight on this issue?  I've never had it happen before.

[Steve Werner]

InDesign places PDF files. It  cannot open PDF files.

[Steve Werner · Accepted solution]

Also, you place (File > Place) an AI Illustrator file. You don't open it (File > Open).

[Willi Adelberger]

AN AI file is technically a PDF file and is seen as such one.

As other wrote, do not open but place external files.

[BobLevine]

If you are placing them, use show options when doing so. There may be a setting in there that won't apply to your file which can throw this error. That setting is sticky.