Gaps in user column in logs - users not matching policies

[thomasd1]

For about 4 weeks now i have started to see some gaps in the Logs for forward traffic.

some logs with the gaps are matched to IP's of user machines, but they are getting deny all as it cannot validate a policy against a user.

FSSO is setup and looks to be working correctly, the only thing that has changed was a change of certificate that we were using for SSL Inspection as we reconfigured our NPS server.

I am at a bit of a loss at what else to look at.