Error while configuration discovery of F5 LTM Device On BIG IQ

OK - so to clarify, you can retrieve a list of virtual servers via rest outside of BIG-IQ, you can get from big-iq to big-ip so maybe check the login username and password are correct and try again. If it still doesn't work, run tcpdump to capture what is happening - it may be that there is an SSL issue or suchlike but it's hard to tell without the details.