Have you done tcpdump to see if the F5 sends the data to the servers and if they return reply as you may have a ping but a specific port could be blocked (you may also use telnet command from the F5 device to check if particular port can be accessed on the IPS server):
https://support.f5.com/csp/article/K411
https://support.f5.com/csp/article/K13637
Check the port lockdown on the self ip that connects to the IPS servers just in case:
https://support.f5.com/csp/article/K17333
Also check this article SSLO issue investigation:
https://support.f5.com/csp/article/K13637