To recreate the issue you have to have MultiMC - Download OptiFine HD U H1 1.17.1 - Extract to the MOD variant - place the MOD jar in with MultiMC 1.17.1 Version folder - hit play - OptiFine is ...
Just picked up the new 1.17.1 stable "OptiFine HD U G9" to upgrade, since I've been running 1.16.5. Without optifine, 1.17.1 runs fine. Once I installed optifine and selected it in the launcher, the ...