Can't suggest mod, invalid URL

For some reason when I try to suggest a mod, it says it has an invalid URL. I looked at a couple other threads and the requirements to see if I could fix it, but nothing seems to have worked.

Here's the mod I'm trying to suggest:

Graverobber's Curse - Mods - Minecraft - CurseForge

Could someone explain the problem?

Quote from Hammercroft

I think the issue is with the mod being new.
Even if it does mature, I don't think it's popular enough to be added to Aternos.

Someone had suggested a new mod, and they also had this same issue.

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There's a chance it's because of how new it is, but I don't think the popularity of it is completely certain since it gave me the 'Invalid URL' error message and not the 'Not Popular Enough' message. I'll wait before suggesting it again.