This seems to be an very interesting error which one may receive while running DBCC ShrinkDatabase command.
The full error is as follows
Cannot use the PAGE granularity hint on the table “tablename”because locking at the specified granularity is inhibited.
The error occurs when you have one or more non-clustered indexes created on table without a clustered index on table. One should always create a clustered index on table, without which it does not make more sense.
The resolution for above error is just to create a Clustered Index on the table on which you are getting error. Will try to dig in and get more info so as to what exactly causes this error and will update you all.
Hope this information is helpful.