For about 12 months, I have been using NextDNS (after a recommendation by @michaelmurfy )  but in the last few days, their second DNS server can no longer be pinged (45.90.30.89)

First server (45.90.28.89) is fine.

A tracert seems to get to Australia but no further.

Interestingly, a ping to the DNS name produced these results - 

Any clues where I should look next?  any other Geeks with this problem?

Cheers.