AWR collected in one rac node, not in the other rac node

Hi all,

my situation, in a 2 node rac environment.

one day, the first node was rebooted automatically caused for some reasons, after that, I found  awr is collected normally at the first node, there is no awr for the second node anymore.

check from os, I find there is mmon process at the first node, but there is no mmon at the 2nd node.

how to fix this issue.

maybe restart instance at 2nd node, I can fix this issue, but you know, it is prod environment.

thanks.