Can someone help me ???
Not with the amount of information you’ve provided. Have a read of these in the Technical Support forum and then supply more information about when you’re getting this error and which of the steps you’ve taken to try and fix it…
Hey, I’ve the same problem. I tryed all of these steps already and still doesn’t works 
"Posted by Drakuloth
Hey folks,
We’re checking to see what’s going on here at the moment. It looks like there are a number of you having this issue. We’ll update you once we get some more information on this, but I wanted to let you know we’ve heard the reports!
Update - Some players are mentioning that if they follow this process they are able to create games again:
- Log out of the game and battle .net application
- Log into EU Battle .net
- Log into EU Diablo III
- Log back out of the game and battle .net application
- Swap everything back to the Americas region
Does this let you work around the issue?"
I succeeded. I just went out of account I changed the password and now it works. Thanks for trying to help me.
This is a troubleshoot article for the error 315000:
If you have already tried the steps and still got problems, then create a topic on Technical Support forum or enter a ticket.
https://eu.forums.blizzard.com/en/d3/c/technical-support
https://eu.battle.net/support/en/help/product/diablo3/273/277/channels
well,
I tried everything!!! I read all the blues about what needs to be done and I did all those things. Logout - log back, change account password, change region and back - nothing, pffff
My “START GAME” button just stays grey saying “only available for party leader”
What now? (never played in group…)
34th relog-change region back and forth- and pw change again solved it! 
Thanks for your help Drakuloth and Maskraider!