fillable pdf calculations work for me, but not my customer

These aren't Acrobat formulas; JavaScript support is part of the PDF specifications (which are public and freely available). But unfortunately, nothing obliges a software publisher to support all PDF specifications in its software.

The same goes for PSD or XLSX files, if you open them in software that only partially supports their specifications, you lose many of their features and capabilities.

This is what I've found since the "Cloud" has been in extensive use by folks.  I develop lots of Adobe Pro Dc forms with extensive formulas.  If this file is sent from the Cloud/Google Drive/One Drive, the formulas do not work correctly *and* if the file is retrieved from Cloud/Google Drive/One Drive, the formulas will NOT work correctly.  However, if the file is saved/sent from your hard drive to another and the other party uses the form file from their hard drive, there are NO problems whatsoever and all the formulas work fine.  So what's the deal on this?  What is going on with Adobe Pro DC formulas seeming not being compatible with the Cloud/Google Drive/One Drive?   We know this is the issue, because we have tested it by asking others to NOT open the file or save the file in the Cloud/Google Drive/One Drive then use the form and it worked FINE.  Happens when these forms are sent, retrieved, or saved to the Cloud/Google Drive/One Drive.  Formulas do not work correctly.  Why is this happening?   Thanks. 

First, you must be sure that your client uses Acrobat to open this PDF.

Many low-end PDF readers do not support these functions, embed the form in a PDF-Portfolio to force the user to open it with Acrobat.