Hello there and I am sorry if this was asked before.
Basically, some mods do not show up on Aternos mod search, even if they are available on CurseForge.
I know such a problem appeared for me with the Twitch Desktop mod downloading. Usually such mods are either new or have quite a low amount of downloads, but I am still not sure about that.
Examples that I know of:
Metal Barrels, relatively new, not very popular, the mods search yields no results. Link to the mod
ComPatchedStorage, an old one, has a lot of downloads, but is a fork of another mod, still nothing. Link to the mod
HunterIllager, quite old, has a small amount of downloads. Link to the mod
Is it the problem with these mods' license or whatever? I would really like to know.