I find this problem sometimes when putting new materials into the machine. I find heating the extruder head first, then selecting insert new material helps get the extruder head very hot… Also snip the end of the new material so its dead straight, if you insert it and its not the ‘gear’ can skip as you video shows. I hold the new material and gentle push feed it through.
If it starts to skip and wont accept then go to ‘remove material’ mode as its likely that the gear now stripped a flat area on the material length. (which means it can grip and pull it through) Cut this away and try again.
Some times you can get a block in the Brass extruder but I’ve only had that once and not likely if you’ve just started.
If it stopped during a print, the material could have got stuck on the reel. Some times it can become snagged if your not careful so check for that too. I’ve had this twice, its quite easy to loop the material wrong on the reel so its get tight after a while, check the material has no ‘ties’ or tight spots as you pull it out.
A good resource is the Zortrax Website if you haven’t already check that.
Hope some of this helps,