Automerge job will not execute match job. Can you please check if you executed the AutoMatchandMerge jon instead? This will trigger the match job first followed by AutoMerge job.
Also, you can query the C_REPOS_JOB_CONTROL table to confirm if the match job was executed or not.
The automerge job will not run match job internally. The situation you mentioned can happen if you manually updated the match rule numbers in the MTCH table before running automerge, but maybe somebody made some changes to the match rules from hub console and saved them (which prompts a message that matches will be reset in MTCH table - this can change the match rules' rowid) and thus the match rule number got changed in the MTCH table after running automerge.
Data from c_repos_job_control will also help to check if you triggerred only automerge job or auto match and merge job (in this case, it will trigger the match job)
Thank you, Kunal and Anuvinda for input. I revalidated the match job. It is working as expected. It looks like there was some issue with the sequence of execution.