If the status stays on
“aggregating” (translated into English) for several hours, it means your account has been flagged as suspicious—but it hasn’t been banned. That’s exactly what happened to me.
I asked customer service about this issue during the previous Arena, before this one was held. They told me my account was flagged as suspicious on
xx xxx xxxx.
I assume that’s why I didn’t get a rank in the Arena.
After doing some searching, I found out that the date matched the Frieren Collaboration event.
At that time, I dealt
0 damage in the new event mode just to obtain the Grimoire Journal

. I think that’s what triggered the flag.
Maybe your case is the same as mine.
Update: I still don’t have a rank in today’s Arena.
My conclusion is that my account is flagged, so I can’t enter the leaderboard in Arena—but I can still play the game.
I just have to be cautious when using the mod.