Just did this Training Mission myself; my steps, after the setup and powering on of the Mavs, uncaging them, etc:
A/G Mode
TGP SOI - Point Track your Target - “Handoff in Progress” displayed
In 4.34, I used to receive an Avionics error at this point. However I did not notice it this time around, to continue with the process:
WPN SOI - Slew cursor to same target as TGP - TMS UP to Lock.
BSGT displayed, click it, it will flash momentarily.
Remove Lock from Mav and TGP with TMS Down when SOI.
Point Track another Target with the TGP, the Handoff should now complete succesfully and display a C above the Station Number.
Repeat for the other Pilon.
This should sort it