I have a spreadsheet with multiple userforms, some very big, and many macros/subs. It is used by a friend in his framing business to price new orders and keep track of customers and existing orders. I am trying to split the file into two (ORDERING and BACKEND) so that he can have the BACKEND open to work on the individual orders and the rest of the team can run the ORDERING system so that they can take new orders. The ORDERING system opens a read-only copy of the BACKEND system when opened so that it can read in the product details for drop-downs on the order forms. This works fine on my Windows machine (Excel 2013), although I do occasionally get 'Out of Memory' messages if I have both files open for a long period and it tries to close the BACKEND via code. I am using the 'Auto_Open' sub when the file opens.

But when I try to open the file on Mac (Excel 16.30) and enable macros it throws up a Compile Error, just saying 'Automation Error'. If I open the file without enabling macros and try to Compile the project it highlights this sub, which is just monitoring two cells on the home page and displays/hides two buttons depending on whether any text is in those cells:
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But even if I comment out this sub, the compile still fails with 'Automation Error', but doesn't highlight anything else.

Any ideas? I will upload the files if it helps, but will take me a while to anonymise the data so thought I'd ask for any general ideas first.