Theja
Why comment on your own post saying you have the same issue??
Anyways, v1.15.2 is out of date and no longer supported. Please upgrade to v1.15.6.
Regardless, if you don't have the ost_user table then someone deleted it. The only way to recover it is to load the data from a previous backup. If you don't have a backup then you will need to manually create the table or do a fresh install.
Cheers.
