Hi Erick,
SNMP agent would poll data from the CIMC, if either of them isn't responding, then you won't be able to see the content you are trying to poll.
This is similar to say, when we aren't able to see specifics regarding HDD's (for example), CIMC monitors all of these details and a restart of CIMC most often does the trick, CIMC works in a similar fashion with SNMP as well.
Is this a one time occurrence, or is this happening frequently?
If it is happening frequently, can you please specify the duration?
Thanks,
Majid