The 3mf uploads do not work right now.
You need to use a different service, like WeTransfer and share the link here.
You could instead read my answers in this topic, which answer the same questions you have.
https://forum.bambulab.com/t/text-being-covered-up/166646/19?u=malctheoracle
This is the link to the first one, the next is down a short bit.