Hi Maria,
The STOP entry in the queue in SMQ1 is not the reason for the problem. Whenever a request load is performed an STOP entry is set automatically in order to prevent data inconsistencies. After the request has been executed successfully the STOP entry is removed again.
However, when something goes wrong with the request, the STOP entry is not removed. This is what you found in transaction SMQ1. From the name of the destination (CRMPRD001) I'm guessing that your problem occurred in a production landscape. Therefore, you should remove the STOP entry in SMQ1 an restart the queue R3AD_CUSTOME* in order to avoid further problems. As long as a STOP entry is present no further BDocs will be processed via this queue (i.e. in your case no BDocs related to customers will be sent from ECC to CRM).
Regarding the root cause of the problem you should first check two things:
1.) Is the request you executed correct? Did to enter the correct selection criteria? Some replication objects, for example, require that the object ID is entered including leading zeros. You should double check this e.g. by executing the same request in the test system and check its results there.
2.) Did an dump (ST22) occur in ECC during the processing of the request?
Hope this helps,
Christian