Mods Installation issue

I have made a server in aternos last week and I installed pixelmon generations and it comes with the biomes o plenty mod. I also added some other mods like set home waypoints and backpacked and it worked well. Just yesterday I reseted the server because I realized that the biome o plenty wasn't functioning properly. I managed to add the pixelmon generations including biomes o plenty mod but I can no longer add the other mods I had. Whenever I try to install it the mods wouldn't appear in the mods folder, I did try to join the server trying to see if it would be in the server but it wasn't there. Is there any fix for this?