Hello,
I have some troubles when adding subnet types, as you can see below :

I have completed all the fields of my new subnet type and it returns me that I didn't.
Moreover, I have tried to add a DHCP Failover Group and it also returns me something strange. When I write my primary and secondary servers, it always returns me that primary server doesn't exist (I checked that I write well my server name) :

Did you ever notice these points ?
Thank you in advance for your response