If you can't dispatch a job to a carrier and modify carrier details, most likely this carrier is inactive on FMCSA or recently was inactive. You can update his status using the link below. After that you will be able to dispatch.
Check the link below
When you can't find carrier, please would plug in DOT of carrier instead of XXXX that will refresh the DOT status of carrier live
Example:
I have a carrier w USDOT #3465057
I'm using that link
https://www.carshipio.com/
This message will pop up, means that he is good to go and status from FMCSA was updated