You should proactively check the current size quota for your databases, to make sure it is set as expected. To do this, the following statement can be used in the context of the target database:
SELECT DATABASEPROPERTYEX(DB_NAME(), 'MaxSizeInBytes');
To solve this issue scale up to the service objective with a larger maximum size quota, explicitly change the quota to match the maximum by using the ALTER DATABASE … MODIFY (MAXSIZE = …) command as shown above (unless a lower quota is desired to guarantee being able to scale down in the future). The change is executed in an online manner.
ALTER DATABASE DB1 MODIFY (MAXSIZE = 10 GB);
On this documentation you will find a table that shows the resources available at each service tier, including the maximum storage.