As I wrote in the thread you referenced, @tmarois:
The most common cause of add-a-solution incompatibilities is the
Categoriessheet. There are two versions of this solution: one that includes a monthly budget for each category (this one is included in the Foundation Template) and a simpler version without budget values. If your spreadsheet contains the simpler version without the budgets, but the solution you wish to install requires category budgets, the solution will be flagged as incompatible.
It sounds like you are using the version of the Categories sheet without the budget periods included. Are you using the Envelope Budget with the Tiller add-on? If you are, your best bet is to create a new Foundation template and follow the migration process that I have documented here.
Once you’ve created the new Foundation sheet, linked accounts, and migrated your budget using the workflow, you could also use the Migration Helper to pull over your categorization and other data from the source sheet.
I hope this helps.
Randy
P.S. I hope you don’t mind that I moved your question to a new topic, @tmarois.