Of course my character is not level 1, either a warrior.
I moved a multiplayer save file from my old original Diablo installation, which is a lvl 36 rogue.
When I connect to battle net I can normally select the character, but in chat channel, my character is displayed as a lvl 1 warior.
Moreover all other players (though there were only few) I saw on channels were displayed as lvl 1 warrior.

It is not only a display issue, because I cannot join L30+ channel, or the Rogue only channel.
I did not do a rigorous test, but trying to enter a hell difficulty game failed as the battle.net thinks I am level 1.
The weird thing is that it was possible to open a hell difficulty game myself, and in the game my character was normal, as I expected from the save file as a rogue.

Has this issue happened to any of you?
I think maybe it is a temporal problem on the battle net server.

Yes, it seems everyone shows as lvl 1 warriors in the chat.

I only joined games in normal mode so far with my old characters, but it seems this new Battle.net realm has new issues the older ones didn't. Then again the older ones don't seem to let anyone create games, so, it's still the best solution we have for multiplayer, I suppose.

I suggest start a brand new, fully multiplayer character, do it lvl 2, and check that.
If THAT works, that means tzhey figured out how to filter the solo chars.

I started a new Rogue yesterday, got it to lvl 12 while playing only on Battle.net, and she still shows up as lvl 1 warrior while in the chat.

I tried it, same problem. Thanks for the clarification.

How did you get onto Battle.net?

I had no problem connecting to Battle.net using the classic version.
Actually getting through "Checking versions" required few retries, but aside from that there was on problem and I was able to get into batte.net without changing or configuring anything.

This is a big problem for me, just got to nightmare but cannt play with anyone because it says im level 1, if anyone figures out what to do let me know please.

You can't do anything about it. It's a server-sided issue and it wasn't there on the old gateway realms of Europe, USWest, etc.

I made a ticket on blizzard support as the lovely GOG support tells you to do, we'll see if they do anything about it.

Otherwise the solution would be to create a private PvPGN server which supports Diablo 1 and works properly.

I received a response on the ticket. They said that I'm the first one who actually reported the issue via the ticket system and that they forwarded the issue to the Development Team and the Quality Assurance Department. So now we just have to wait :)

Its officially fixed!!
We can join game nightmare / hell
+ the lobby now show the class / lvl /diablo killed
HOURAA!