Okay. It's a little confusing. It will be easier for me to find a deal on a 12 month code than a 6 and a 3 or 3 3's but then I would lose 3 months and I might not get the deal. If I didn't do the 3 months of gamepass for $1 in the first place, I wouldn't have this issue but like everyone here, I had no idea M$ was gonna do this Ultimate Promo.
I cannot say for certain as I've not looked at the coding, but the way it seems, it sounds like people were having problems adding over 3 years of Live *alone*. For example, if they had 13 months of Live and zero months of GP, they could add a 12 month code no problem, but if they tried to add a 24 month code - ERROR.
Similarly, say a person had zero months of live and zero months of GP. Bought 3 12month live codes, entered the 1st code on the site, but didnt turn off the 'free month for recurring billing' (i.e. got 13 months). Enter 2nd code, no problem. Enter 3rd code (which would take them to 37 months) - ERROR.
I'm sure that when I converted, I had 34.5 months of Live (got an extra 14 days from redeeming a 1 month code) and 2 months (+six days) of Game Pass remaining from the $1/3mo. offer. With the 1 month that comes with the switching to ultimate, I *should* have been over the 36 month limit combining Live and GP. However, it converted just fine, simply dropping the extra time and giving me a full 3 years of Ultimate.
Take that for what you will.