Unable to update to 2021.1.5 or update add-ons

[richt (Rich)]

Take a look at this. It may not apply, but is worth a try.

Can't install homeassistant:2020.12.0

Go to supervisor than System than under Host System next to Ip address click change than expend IPV4 and change IP DHCP to static and under DNS server add google DNS : 8.8.8.8 Reboot HA and than update supervisor. than update Home Assistant to latest available version.