What version of UIM are you running?
Please use hub v7.92 HF10 or higher.
Deactivate nexec, save the nexec.cfg if necessary and then delete the nexec probe from the local filesystem.
Purge the %NIM_ROOT%\robot\pkg\ready folder of any nexec remnants.
Redeploy nexec
All nexec Tabs should now be displayed.
If not, please open a support case so we can analyze this issue further, as this issue may be due to your hub-robot NAT configuration.
Thanks,
Steve