Hello, this issue happens when in your region there is no new quotas for your database. So you have to ask quotas in "Help + Support".
To check that if there is quota for your database run this command in Azure CLI:
az mysql flexible-server update --resource-group your-resource-group-name --name your-database-name --sku-name Standard_B1s --tier Burstable
You will have this response: No available SKUs in this location.
If you just run scaling for your database it will just show error that your deployment failed.
Also Germany West Central have some troubles with new quotas, so I changed databases to West Europe.