Unable to upgrade snap from 4.1.2 to 4.3.2

[hez55]

Hello, I have an offline rocketchat snap server. I use to "snap download" from a computer, so I can install manually updates on my offline server.
To upgrade from 3.18.3 to 4.x, I managed to install 4.1.2 (snap 1491). Now I am trying to upgrade to 4.3.2, and I have the following message :

>snap install rocketchat-server_1510.snap

error: cannot install snap file: cannot refresh "rocketchat-server" to new revision 1510 with epoch 6, because it can't read the current epoch of 2*

Any clue of what I did wrong ? I never had issues with 3.x versions

Thanks

[radsdau]

I'd really appreciate understanding what this means, and how to fix it. I'm a bit stuck as RC is complaining now that it's going to stop working in a few days unless I update. Stuck on 3.18.7