Right of Purchaser of IPR of Software to get license fees from the licensee of b

An entity was granted a license to use a software by the Licensor as per an agreement which automatically gets renewed every year.

Licensor sold the IPRs in the software to a third party before it became bankrupt. The license agreement was not assigned to the third party purchaser. License fee was paid by the Licensee to the Licensor until the quarter in which it filed bankruptcy.

What are the rights of the third party purchaser of the Software over the Licensee who is still using the software without paying the license fee to anyone? Can the third party purchaser claim license fee from the date of assignment of IPRs to it from the Licensee independently of the license agreement?