It is most likely due to one of two reasons:
1. You didn't log into quay.io. Now, this could be because you used the incorrect password. Since Red Hat converted quay.io to SSO, there is one password that's used to access the site via a web browser and a different password that's used when using the CLI. Here's the instructions I give my students:
Since Red Hat owns Quay.io and they've switched over to a Single Sign On (SSO) procedure, the process to log into quay.io (via the web browser and the command line has changed):
This new encrypted password is what you'll use when accessing quay.io from a terminal command prompt - whether your own virtual machine or the lab space.
You'll still use your normal password when logging in through web page.
2. You may need to make the nexus repository public. By default, it is created as private. This involves logging into the quay.io website. When you do and if you see this:
You then click on nexus (it is a link), then click on:
Then scroll to:
Paste more info, including the actual command -- you snipped out too much from your screenshot for us to know more.
Based on the FEW lines of error, you are running 'podman pull'? against quay.io? So
podman pull quay.io/ubi8/ubi:8.3
UBI8 tag 8.3 is on registry.redhat.io, and that is a private registry that requires authentication. You'll have to successfully run a login with your creds, so:
podman login registry.redhat.io
to use anything from that registry.
Or if you're pulling from a public registry, then podman shouldn't generate an authorization error.