Yet another XP for workouts thread but I couldn’t find any definitive answer on the web.
I know how XP are awarded after completing a block but yesterday i had an 2:45h Z2 block and had to skip it after 2h (because of time constraints irl^^). While I did get points for warm up and cool down I didn’t get points for the 2h block. Is this because I skipped it? Never had to skip a block in all the years 
If that’s a custom workout you might try breaking it up into 15 or 30 minute segments of Z2 blocks back-to-back.
Edit to add: It stinks that you lost all that XP. Sorry man!
You only get XP when completing a block in workout mode. If you skip or stop mid-block, no xp will be awarded.