Complex form too complicated?

[Bahstan Rob]

Hello, All and Help!
I've been using Access versions for about 30 years though I would never claim that I know my left foot from my right even on a good day. I recently got Office 2019 Pro 64 bit and downloaded it to my laptop which uses Windows 10 as its OS. I have been building a form to input information about my library which runs about 3,000 books. For that comprehensive form I have built a number of sub-forms all of which seem to drag and drop into the primary form easily except 1, the form to include information about the author. Kind of major bit of information, I think. I have jiggered and rejiggered the sub-form but I always get the same message when I try to bring the main form up in Form View. That message is as follows

"This expression is typed incorrectly, or it is too complex to be evaluated. For example, a numeric expression may contain too many complicated elements. Try simplifying the expression by assigning parts of the expression to variables."

It would be helpful if I knew what that meant but even more important is the fact that there aren't any overt numerical expressions in the sub-form. There are 12 combo boxes in the sub-form although I have disabled 2 of those in the hope that my sacrifice to the Gods of Access might allow them to smile upon me and allow the sub-form to work. Also, let me note that the sub-form shows up just fine in Design View but is just a big blank space in Form View. The Label shows up in both views, but not the sub-form itself.
I admit to being more than a bit of a dunce and apologize for annoying any of you reading this question and wondering why I'm incapable of seeing what is probably a simple solution. I also thank anyone who responds in advance for any help you can give.

[Welshgasman]

I think you would have to upload the DB and give explicit instructions as to which form etc?

I'm off out right now, to pick up a passenger, but should be back in a few hours.

No doubt someone else will have answered by then, but I still think they would need to see the DB?

Plus they would need a 64 bit office as well? Mine is only 2007, so 32 bit.

Good luck anyway.

[Minty]

What links the main form and the troublesome sub form? E.g. what are the Master Child properties set to?
What is the record source of the sub form?

Other than that post a stripped down version of it with enough data to replicate the problem.

[Micron]

"This expression is typed incorrectly, or it is too complex to be evaluated. For example, a numeric expression may contain too many complicated elements. Try simplifying the expression by assigning parts of the expression to variables."

You can generate that message by simply excluding a separation character such as , ; ) and the like. When that is the cause it makes Access think a portion of an expression or sql statement cannot be resolved.

[orange]

As others have suggested, it could be as simple as "punctuation" or something very serious. It might be easier if you posted a copy of the database so readers can experience the issue. Any specific instructions re the form or purpose of offending subform(s) would also be helpful.

[Bahstan Rob]

Thank all of you who responded. I took your advice and have managed to solve the problem. Now all I have to do is find a few fields that seem to have wandered off on their own and are resisting my efforts to locate where they are hiding. Or perhaps the fairies and gnomes inside my computer are just playing hide and go seek with me. In any case, problem solved! Thank you all.

[Micron]

It's customary to post your solution so that others who are having the same issue and read your thread might learn by your example.
Upon reading your last post, it seems I missed this

Also, let me note that the sub-form shows up just fine in Design View but is just a big blank space in Form View

You're probably referring to this issue:
http://allenbrowne.com/casu-20.html