Following are the possible reasons:
1)WS not generated for 1 year or more before and after the date when the error occurred.
2)View V_551C_B: PWS not assigned to a WS valuation class
3)Employee has been transferred to a different PA/PSA, EG/ESG resulting in change of groupings (ESGG or PSAG), or Holiday calendar but the WSR has not been changed to a valid one applicable for the new keys. This is a common error where a Time admin person has skipped changing WSR during the transfer pers action.
It can be checked by going PA20 or PA30, select IT 7 for the time eval date where the error occurred. In the WSR field, press F4 or look for possible WSR keys. If the existing one is absent, copy an existing one with the WSR to the new key values, generate the WS, etc, copy the transport in SCC1 txn to the dev test client. check if the time eval error disappears with similar data as you found before. Then move the transport to the relevant systems/clients.
Hope this helps.