virtual domain IP changed and when tried to change back won't work

I had one of the domains I host that I changes to x.x.x.51 which was an offsite separate server and now want to change it back to x.x.x.50 which is the address of the ISPCONFIG3 server but the IP is still resolving to the x.x.x.51 address and not x.x.x.50 even after resync and reboot. I saw it was suggested to flush DNS cache with systemd-resolve --flush-caches but can't find the program to install. Not sure what to do here. short of deleting the whole domain. I don't want to do that because I don't wan to loose the websiet.

Any ideas?

 

Ever heard of time-to-life? That determins the cache refresh in dns servers all over the world.
You can clear your own local cache on your computer, but when the cache of the dns server you use for resolving isn't refreshed it's useless to clear just your own.
You probably just have to be patient.
There are several sites, like mxtoolbox.com, where you can do all kinds of tests on your dns zone. If your change is ok in that test then you just have to wait.

 

Yes correct. It resolved thanks!