This is what they sent me:

Waarom is mijn account gesloten?

Op basis van onze beoordeling hebben we vastgesteld dat je onderneming een risiconiveau heeft dat buiten onze acceptatiecriteria valt. Zoals beschreven in artikel 4.1 van onze Gebruikersovereenkomst kan Mollie haar diensten weigeren of beëindigen wanneer een onderneming niet voldoet aan onze risicovereisten.

Translation:

Why has my account been closed?

Based on our assessment, we have determined that your business presents a level of risk that falls outside our acceptance criteria. As set out in clause 4.1 of our User Agreement, Mollie may refuse or terminate its services if a business does not meet our risk requirements.

I guess they are referring to this paragraph in 4.1:

Mollie may also decide, at its own discretion, to decline products and services that are not explicitly mentioned on the list, but which pose an unacceptable risk to Mollie based on its internal policies.

But I have no idea why i am considered unacceptable risk?