ModCoupler-Verilog in the current version of PSIM is compatible with all versions of ModelSim (64-bit only).
ModCoupler-VHDL in the current version of PSIM is compatible with Questa Core 10.0 (64-bit only).
ModCoupler-VHDL needs the FLI (foreign language interface) feature to communicate with ModelSim. Nowadays, FLI is a pay-only feature, available only in Questa Core.
ModCoupler-VHDL does not work with ModelSim-Altera nor any other free Modelsim variant.
ModCoupler-Verilog works with any ModelSim or QuestaSim version. The required feature (VPI) is part of the Verilog standard, so any simulator will support it.