ipad pro not saving the manual DNS configuration

Hi,

My iPad Pro is not saving the manual DNS configuration that I'm trying to set up in order to connect to a server located in my local wi-fi network.

Actually what I'm trying to do is to include a local search domanin name.

After ticking the Manual configuration and entering the new search domain name, I click Save, but after this the Configuration DNS is still keeping the Automatic configuration instead of switching the manual one.

I've done the same setting on my iPhone 7 and it worked from the first try.

How can I solve this ?

Thanks,

Emil