I believe the quality of this module went down, since it's no more maintained by Martijn and Michael: https://github.com/mollie/PrestaShop/commit/fb5bd9f287bae5d393a934c21e9244d9d30daa70#diff-a50a9e2177492d1e4d64e6d84a7f8ceb
Here is the update, where it should happen. There arise multiple questions to me:
Why is the prefix mol and not mollie (as mollie_payments table)?
Why is the mol_countries not in the installer sql?
Why was the table still not added, since you both upgraded?
Well since I anway want to leave from mollie, I won't fix any of this ofc.