The previous log may have been from when someone logged in when it was waiting that 300 seconds.  The following log is better:

[2019-06-15 00:31:15.496 UTC] [svservice:P1648:T2072] Computer UUID (Microsoft format): DDB11842-1241-5AEE-539E-E8A94DB300A0

[2019-06-15 00:31:15.496 UTC] [svservice:P1648:T2072] Computer UUID (VMware format): 4218b1dd-4112-ee5a-539e-e8a94db300a0

[2019-06-15 00:31:15.496 UTC] [svservice:P1648:T2072] Initializing HTTP session

[2019-06-15 00:31:15.496 UTC] [svservice:P1648:T2072] MaxDelayTimeOutS configured as: 600

[2019-06-15 00:31:15.496 UTC] [svservice:P1648:T2072] Initializing HTTP connection

[2019-06-15 00:31:15.496 UTC] [svservice:P1648:T2072] Choosing a manager out of 1 configured manager(s)

[2019-06-15 00:31:15.496 UTC] [svservice:P1648:T2072] IsDomainJoinedComputer: NetGetJoinInformation() success, domain name DEVNCSECU and type is 3

[2019-06-15 00:31:15.512 UTC] [svservice:P1648:T2072] Pre-startup URL: Machine Info stuff removed

[2019-06-15 00:31:15.512 UTC] [svservice:P1648:T2072] [0] Connecting to appvolumesserver:443 using HTTPS (attempt 1)

[2019-06-15 00:31:15.512 UTC] [svservice:P1648:T2072] WinHttpSendRequestWithSSLCertValidation: SSL certificate validation is disabled.

[2019-06-15 00:31:15.512 UTC] [svservice:P1648:T2072] WinHttpSendRequestWithSSLCertValidation: WinHttpSetOption(WINHTTP_OPTION_SECURITY_FLAGS) succeeded.

[2019-06-15 00:36:19.521 UTC] [svservice:P1648:T2072] WinHttpSendRequestWithSSLCertValidation: WinHttpSendRequest succeeded.

[2019-06-15 00:36:19.521 UTC] [svservice:P1648:T2072] WinHttpReceiveResponse timed out waiting for response

[2019-06-15 00:36:19.521 UTC] [svservice:P1648:T2072] Retrying in 5 seconds (waited 304 seconds out of 600 max)

[2019-06-15 00:36:24.537 UTC] [svservice:P1648:T2072] [0] Connecting to appvolumesserver:443 using HTTPS (attempt 2)

As you can see the agent waits 304 seconds until it makes its second attempt to connect to the manager at which point it succeeds.  Like I said giving it a whole second try is 100% better, but you have to wait 5 minutes for it to do that.  Unfortunately users can actually log into the VM in that time as Horizon view doesn't wait to make the machine available if app volumes is borked.