There are a number of situations which you cannot resolve by using TSPITR.
You cannot recover dropped tablespaces.
You cannot recover a renamed tablespace to a point in time before it was renamed. If you try to perform a TSPITR to an SCN earlier than the rename operation, RMAN cannot find the new tablespace name in the repository as of that earlier SCN (because the tablespace did not have that name at that SCN).
In this situation, you must recover the entire database to a point in time before the tablespace was renamed. The tablespace will be found under the name it had at that earlier time.
You cannot recover tables without their associated constraints, or constraints without the associated tables.
You cannot use TSPITR to recover any of the following:
Replicated master tables
Partial tables (for example, if you perform RMAN TSPITR on partitioned tables and spread partitions across multiple tablespaces, then you must recover all tablespaces which include partitions of the table.)
Tables with VARRAY columns, nested tables, or external files
Snapshot logs and snapshot tables
Tablespaces containing undo or rollback segments
Tablespaces that contain objects owned by SYS, including rollback segments