I don't know what email services (work or home, Gmail, M365 or Outlook etc.) you're using or if its all of your email or your Outlook is screaming for one of multiple accounts so I'll make some assumptions that you use one or more:
M365
- Microsoft deprecated POP3 because its considered legacy authentication as it doesn't support MFA (multi-factor authentication). MSFT disabled it for all tenants in late to early Dec 2022/Jan 2023. If this is it, its bombing because you're not supposed to get in.
Outlook
- Honestly, you should stop using POP3 for the above reasons. Implement MFA and then use an app password to better secure your email
- https://support.microsoft.com/en-us/office/add-your-outlook-com-account-in-outlook-for-windows-642c1902-bdd9-4dc3-abe7-76d60b148b23
Gmail
- If you're employing POP3, check your timeout setting to see if its misconfigured or changed. Google recommends 5 minutes with a minimum of 1.
- https://support.google.com/mail/answer/7126229?hl=en&sjid=1792684313790843886-NA#zippy=%2Cstep-check-that-imap-is-turned-on%2Cstep-change-smtp-other-settings-in-your-email-client
Is there a specific reason why we need POP? IMAP is frankly a better protocol to use of the two given that we all check email from multiple devices these days: