User Forms not displaying correctly in MS365 Excel for Mac

I need some help. I developed a simple budgeting system in Excel many years ago, which revolves around a spreadsheet with sheets for each account. I built three user forms to allow for a Deposit (which is distributed among the accounts based on data in the summary sheet); Single Entry (which can be either a credit to or debit from a specific account), and a Transfer (which takes an amount from one account and transfers it to another. Here are pictures of the three User Forms as displayed on my Windows machines (whether running Office 2019 Excel or MS 365 Excel for Windows):

The key is that the Single Entry and Transfer forms display a list of accounts that can be selected from. The problem I am having is that when I try to do this in MS 365 FOR MAC, the lists of accounts are not displayed and cannot be selected from (only a blank box appears).

The Deposit form, which has no list to select from, works perfectly fine, so it's not a general problem with macros. Fortunately, even after the file is opened and edited on Mac, it can be reopened back on a Windows machine and still works properly there.

I know that there are limitations in Excel for Mac with regard to building User Forms, but I didn't see anything specifically described that would create this situation. I'm wondering if perhaps it might be a font issue??  

I built these years ago and have used them for many years without problems. I'm pretty sure I can come up with another way to do this, but I was hopeful that someone out there might have a simple solution for me??  I moved from Office 2019 to MS 365 specifically to allow me to use a Mac, so this is really throwing a monkey wrench in my plans!!!

Thanks to all for your consideration!!