What infrastructure and endpoints are you using, as well as software versions for each?
I know you're using an MX800 from your other discussion here and I presume have the endpoint configured per the presentation slide desk I linked to. Did you check the other pages, regarding other required settings to get it working?
Required servers, versions, and special settings if any.
Beyond trying to help make sure you have the correct server versions and settings, as I don't have CUCM, I can't help do an actual test.
CUCM - 11.1
Conductor - 4.0
VTS - 4.2 (4.18)
SX80 (off network coming through VCS-e) ce8 beta10
MX300G2 - ce8 beta10
MX700 - (off network coming through VCS-e) 7.3.3
It is a rendezvous number, and when I dial the SX80 in it shows up as Standard for Type on the VTS. I didn't know if the initial SX80 call coming through the VCS would hurt it or not. I can setup a different scenario if need be. But confirmation that the beta ce code will work, will help.
Multistream is not currently supported correctly through the Expressway, which will explain why the SX80 isn't working. As for MX300G2, the beta10 CE8 code should work with the 4.2(4.18) you have set up but there are a small number of hoops to jump through
I'd recommend contacting your EFT contact for CE8 with regards to getting this set up. They should be able to take a look at the Conductor and CUCM settings to check that the IX and multistream protocols are making between the TS and MX300 end-to-end.