When a request in ComCat is created, a list is built of all possible lenders.
Sometimes there may be an error with the lender list that was automatically built, or a lender needs to be added to the list. A common cause is if a new lender of the item is added to the system after the request was originally created.
For reading and manually editing the lender list, please see this guide: https://flo.libanswers.com/ComCat/faq/270890
Rebuilding the lender list:
Staff at the borrowing library may rebuild the lender list on a request if needed.
Open the request in full record display, and scroll down to lender list:
Click the "rebuild lender list" button. 
Select "OK" when asked for confirmation.
The request will go to Awaiting Lenders status, and if lenders are found and the item is available, it will soon move to Pending with a lender. This may take a few moments. *
If no lenders are found or lenders are found but the item is not available, the request will return to Retry/Unfilled.
*If your request does appear stuck in Awaiting Lenders status for more than several minutes but it shows a lender list, you may try "Add Lenderlist" and submit.