Snapshots Reserve

Hello All,

I am using Dell Equallogic 6510e with 104 TB space as total & free as 78 TB, (3 Members)

We have created multiple volumes, out of which I am having problem with one volume, the snapshot schedule was running well until this 22nd March 2018, but from 23rd March 2018, i got the following error : - 

Snapshot schedule Daily failed to create a snapshot for volume XXX; failed to schedule a creation.

we have not created any snapshot schedule, no firmware upgrade, no volume creation since quite long time, also would like to update that we have tried disable/enable snapshot schedule, deleting the old schedule & creating a new schedule with same properties but it didnt work out, also tried to create snapshot manually for the particular volume which is having problem but creating manually also failed.

Kindly assist.

Storage Firmware version is v 3.7

snapshot schedule is daily at 12 am

snapshot to keep is 7