Welcome to the forum.
I understand that Safeguard works by changing the router DNS addresses.
You probably need to go into your router advanced settings and find where the DNS addresses can be set. When you get there it probably has them set to
To revert to the default Plusnet ones change them to :
Others are available as having your own router you're not limited to Plusnet's, for example you can use Google's on 126.96.36.199 and 188.8.131.52. I use OpenDNS on 184.108.40.206 and 220.127.116.11
Don't forget to save your settings if required by your router.
I'm sorry to hear that you've experienced this issue. If you haven't already it's worth carrying out the instructions linked above by @Baldrick1, but if you experience any further issues please let us know so we can take a further look into this.
Thanks for providing these screenshots @MikeHux. Please can you change the primary and secondary DNS addresses around? If this doesn't work, please can you also try to change the DNS address to the following;
Primary DNS: 18.104.22.168
Secondary DNS: 22.214.171.124
OK if @TheMightyAJ suggestion doesn't work the next thing to look at:
Device settings overide those stored in the router. So go into your device wifi settings and under DCHP settings you should find the DNS address. Depending on the device it may be under IPv4 settings. This should be set to the router IP address 192.168.1.1.
If you get stuck come back and tell us what device you are using for more detailed advice.