Root Cause:
Check the Approval Debug logs for the request if you find logs like in the snippet like below :

• Wrong "Approval Prcess Name" given in Workflow in DWPC
• Spaces in the "Approval Process Name" either in DWPC or in ITSM Approval Process
• Copy paste the Approval Process Name from One Place to Another Place in DWPC "Approval Process Name" Examples are as below :

E.g. 1. Incorrect Approval Process Name in "Process Name" parameter in Workflow


E.g. 2. Incorrect Approval Process Name populated in 'Questionnaire'


Solution :
You can navigate to the above sections and try to give the CORRECT 'Approval Process Name' typing manually and save and Re-Publish the Catalog again.

If there is still an issue then follow the below steps:

1)Login to Mid Tier and open process in the Approval Administration Console

2)Open the impacted process and note all its Rule names

3)Manually type the process name and save it by adding 1 at the end of the process and then remove 1 and save again

4)Now since the process name is updated so Rules might be missing 

5)Without selecting a process from Approval Administrator Console, Navigate tothe  rules section and open all noted rules for the process from step 3

6) Manually select all required fields from the rules and save

7) Now Rules will appear for the respective process and the issue should be fixed