OptiFine_1.16.5_HD_U_G8_pre9 is just not there
There is OptiFine_1.16.5_HD_U_G8 available on the official optifne website
And optiforge's latest version of 1.16.5 needs OptiFine_1.16.5_HD_U_G8_pre9 if you wanna
Play with optifine in forge pls give an solution for this