Migrating from Slack

I’ve been trying to migrate from Slack to mattermost for a few days now.
I checked how it should be done on the documentation, I tried using the web app and the CLI but none of these works.
Some channels actually made their way to Mattermost (Some channels have parts of their content some have none), some users have also been imported but that’s pretty much it.
If you have any ideas of what may be wrong, I’ll take it.

What server log errors do you see? What Mattermost server version are you on?

When we tried the webapp it just didn’t work, we tried several time and I think it’s because the Slack export had more than 10 000 messages, so when we tried with the CLI it told us our team didn’t exist.
And we’re on Mattermost 5.24.2

We actually managed to fix our problem, the team name was not set right in the beginning.
Thanks for your help.