I was seeing if I can get the promotion trial for one of those Google music service for getting a GHM, but found there was no offer available.
ref: https://support.google.com/googlehome/a ... 4?hl=en-CA
The chat told me something along the lines of I had a GPM subscription before, or I had redeemed the trial previously, so that's why I couldn't get it.
He suggests that if I were to try this again, to setup the GHM on a new Google account first, then I can redeem the promo, then I just unlink the GHM and link it back to the original main account after.
Figured I throw this out here in case anyone wants to get more out of their GHM.
I haven't tried this out myself yet, but don't see why this wouldn't work.