E-mail log in details, pop & smtp all correct - but since testerday cant log in - says password & log in details incorrect. Have tried re-installing no joy.

E-mail log in details, pop & smtp all correct - but since testerday (23/09/15) can't log in to this account on thunderbird - says password & log in details incorrect which they are not. Have tried re-installing thunderbird with latest edition - no joy. Have tried deleting this account & re-installing it - no joy. My other e-mail account with same ISP is working ok. Have contacted ISP - followed all their checks - (ISP = Sky) - can log in to e-mail account with them but none of my e-mails show up in that account other than the welcome e-mail goingn back over a year - nothing else. Any asistance appreciated. Thanks.