Error while entering Opportunity

Hello. Today I started getting the following error while entering a new donation. We are running NPSP and have not had this issue until today. Any help would be greatly appreciated.

"OpportunityTrigger: execution of AfterInsert caused by: System.DmlException: Insert failed. First exception on row 0; first error: CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY, kell01.AllocationTrigger: execution of AfterInsert caused by: System.DmlException: Update failed. First exception on row 0 with id 0064p00000U3vjSAAR; first error: CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY, npsp.TDTM_Opportunity: execution of AfterUpdate caused by: System.StringException: Invalid id: Membership Class.npsp.RLLP_OppRollup_UTIL.setupRollupVars: line 215, column 1 Class.npsp.RLLP_OppRollup.<init>: line 53, column 1 Class.npsp.RLLP_OppRollup_TDTM.run: line 60, column 1 Class.npsp.TDTM_TriggerHandler.runClass: line 193, column 1 Class.npsp.TDTM_TriggerHandler.run: line 113, column 1 Class.npsp.TDTM_Config_API.run: line 92, column 1 Trigger.npsp.TDTM_Opportunity: line 33, column 1: [] Trigger.kell01.AllocationTrigger: line 75, column 1: [] Trigger.kell01.OpportunityTrigger: line 58, column 1"