Personal Facebook-Accounts as Agency

An issue with setting up a Facebook Business Page for a client:

The client got Instagram all set up himself, but wanted our help with Facebook because it was too complicated. Turns out it was too complicated for us as well. 🙂

Setting up his business manager and business page was easy. However for him to be able to post his Instagram posts on Facebook, he also needs a personal account. Okay, he set it all up himself with his own real data and gave us his login details.

We connected Instagram with his fb-account and then his fb-account with the business manager. At which point Facebook banned the fresh account. An appeal did nothing.

What exactly went wrong and what would be the correct way to handle setting up personal fb-accounts?

We want to help our customers as much as possible since they usually have no clue about how this all works.