VM has been making the changes now for some time under the banner of 'security'. You may be 'nudged' into the changes by VM and this often seems to happen when you make a change to your setup (although sometimes it happens with no changes at all).
When you use an email app on a device you will be required to provide an app password (which you generate from within 'My VM' for the mailbox in question) as explained below
https://www.virginmedia.com/help/broadband/manage-email-settings
When you set up an email app you use your VM email address and the app password for the setup along with server settings from the above link
As part of the above process you may also be asked to provide a third party email address (such as Gmail etc.) to run alongside the VM mailbox.
Once you have provided the third party email address you use that along with your VM password to access 'My VM' and VM webmail.
Refer to some of the other many past topics on here for further explanation.
(Some have found when trying to provide a third party email address that they get stuck in a loop of not receiving a verification email. If that happens you will need to post back for help from the VM forum team).
