Because IPB 2.1.2 is nearly 20 years old, it is incompatible with modern server environments like PHP 8.x. Instead, consider:
Invision Power Board 1.x?/2.x/3.x - Admin Takeover - Exploit-DB Invision power board 2.1 2 nulled
Released as a maintenance update, version 2.1.2 focused on refining the substantial changes introduced in the 2.1 series: Because IPB 2
A complete overhaul of the administrative interface to improve management efficiency. Invision power board 2.1 2 nulled