Unable to receive e-mails from multiple sources

I am unable to receive e-mails from various places, regardless if I add their email address to my address book, check spam folder, check e-mail filtering settings, and more. E-mail forwarding does not work either. I have had this issue since 2023 and have not yet been able to resolve it. It has caused the inability for me to sign into multiple accounts in which I have used my comcast e-mail.