F5 r10800 not connected to Cisco Nexus 9000

Maybe as mentioned for VELOS Configure LAGs with LACP between the VELOS system and Cisco Nexus 9000 series switches make certain that the LACP interval is "slow" if it is not a bug as it was mentioned. Also check the port groups are correctly configured rSeries Networking

We experienced the same issue with F5OS-A and the R5000/R10000 models, where the interfaces wouldn't come up. When configuring LAGs with LACP, the LAG took about 2 minutes to come up. We opened a support case, and an EHF was developed to fix this in version 1.7.0.
After applying the EHF, we noticed an improvement in the interface and LACP bring-up times, although the stabilization time is still not the ideal 5 to 10 seconds.

A bug was identified for this behavior.

https://cdn.f5.com/product/bugtracker/ID1365821.html

https://techdocs.f5.com/kb/en-us/products/f5os-a/releasenotes/related/relnote-supplement-f5os-a-1-7-0.html

do you use f5 sfp on cisco side?
if yes, you need to allow 3rd party module on it, such as
https://www.cisco.com/c/en/us/support/docs/interfaces-modules/gbics/200296-Unsupported-GBIC-SFP-in-sub-module-of.html