Yes as per details received, it looks like 1.2 failed which was part of disk-group Group1 and 1.15 was configured as Global spare. The moment 1.2 failed, 1.15 got used to reconstruct data of 1.2 so 1.15 now part of Group1 means part of Pool A
As informed you earlier, It seems better to get SMU V3 Homescreen screenshot to understand how much is Reserved space (RAID Parity and metadata) because this space will be taken from disk-group space only.
You don't have sufficient space to convert Thin Volume to Fully provision volume or Thick Volume that's why you are not getting overcommit disable option.
You need to add more drives and make new disk-group like Group1 and then add it to Pool A. It's always recommended to add same number of drives and configure in same RAID like existing disk-group in same tier to get better performance for that Pool. Keep in mind that you can't extend disk-group here like you did vdisk expand in linear MSA array.
Hope this helps!
Regards
Subhajit
I am an HPE employee
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