How to RE-ENABLE IPv6 functionality on Ubuntu 18.04.5 LTS ?

I enter the following command in a terminal to DISABLE IPv6:

for ip_six_devs in all default lo; do sudo sysctl net.ipv6.conf.${ip_six_devs}.disable_ipv6=1; done

This works fine. I can go to https://test-ipv6.com/ and it reports 'No IPv6 address detected' To re-enable it I assumed the following would work:

for ip_six_devs in all default lo; do sudo sysctl net.ipv6.conf.${ip_six_devs}.disable_ipv6=0; done

but it doesn't, all IPv6 test sites still report 'No IPv6 address detected' The only way I can re-enable IPv6 is to reboot my machine which isn't practical. What commands should I issue to re-enable it, also is there a command I can use to see its current status ?

Thanks,

Usjes,