Test Co-Authoring Of Excel Workbook In OneDrive

I need a person who can test the co-authoring feature of Office 365 for an Excel workbook with macros when the workbook is stored in OneDrive. For reference:
https://support.microsoft.com/en-us/office/collaborate-on-excel-workbooks-at-the-same-time-with-co-authoring-7152aa8b-b791-414c-a3bb-3024e46fb104

I created this bespoke workbook for a client with two offices around the globe. The intention behind this spreadsheet was to co-author it with the aforementioned Office 365 feature so that concurrent users would be able to use the spreadsheet and see each other updates simultaneously. The client wasn't able to co-author the workbook and I do not have Office 365 subscription to test it myself. I'm posting this job to find a person who knows what co-authoring in Excel is, to implement and test the co-authoring feature successfully on this spreadsheet.

An added bonus would be if you also know how to troubleshoot OneDrive issues and I'm willing to pay more if you can also test and troubleshoot the client's OneDrive for this co-authoring feature.

My client is using Excel for Mac in both offices. Maybe this issue is only related to Excel for Mac. I would therefor need it to be tested with Excel for Mac as well as with Excel for Windows.

Description of the spreadsheet:
Contacts Database which has 3 sheets for the employees to save and load data (phone numbers, e-mails, etc.). The contacts are classified in 3 types, each in a different sheet. There is a sheet that contains a search interface and another sheet that contains the interface to add a new contact or edit an existing contact. I will provide this spreadsheet to any suitable sellers who will send a proposal for this job.

The budget of this job is just a placeholder, so feel free to suggest the amount you have in mind. If you have the capability to troubleshoot OneDrive issues, please include a separate quote for this as well. I believe that the inability of my client to apply co-authoring is related to OneDrive and not to the Excel spreadsheet. The desired testing is supposed to narrow down to the option that the problem is indeed with the client's OneDrive configuration.

For your reference I attached a Word document with email communication and questionnaire which I provided to the client. The client responses to my questions are colored in red font.