You may have a problem with your VM mailbox or it may just be another problem in the long list of never-ending problems with VM email.
Here is a link from a past topic about the 'forbidden' web page message
https://community.virginmedia.com/discussions/email/403-forbidden-on-webmail-again/5342528/replies/5467926
If you can get into 'My Virgin Media' for your mailbox you should be able to try the password reset.
I believe you have to also generate an app password (even if you do not need to use one with an email client) and I have also read on other password reset topics that leaving a period of time after the reset is important before trying to regain access with the new password. The link above states an hour. I have seen other posts mention 30 minutes.
This is all just more random nonsense with the VM email service. If/when you do regain access you should make a backup of the contents of your mailbox. Mailstore Home is free and gets regular mentions on here.
After that, do yourself a favour and start the process of moving all of your online services away from VM email and onto a third party, non-ISP service which should bypass all of the never-ending problems with VM email.
