Licence first, payments second
Gaming is usually processed under specific gambling merchant category codes, and acquirers apply those codes strictly. Before boarding, providers check your licence, its issuing authority, the markets you accept players from and whether gambling is permitted in those markets.
Operators with a well-regarded licence and a clear list of target markets have the widest choice of providers. Operators whose licence is newer or less recognised, or who accept players from markets where online gambling is restricted, face a much smaller pool. A licence that matches your target markets is the foundation of the payment stack, not an afterthought.