Won't recognise password but web mail will

Been away for 1 week, and not used Thunderbird during absence. On return logged in as usual on desktop and cannot retrieve or send messages on Thunderbird - message asks for webmail password, which it has not done for many years, then will open inbox but only shows all mail up to the day I last shutdown the system (7 Oct), then continues to ask for password for host. Have tried editing password within settings (but it is correct anyway) and can separately log into webmail (using the same password). Essentially unable to use Thunderbird but unwilling to use email history and using the webmail interface (plusnet) is slow and unwieldy. Any ideas much appreciated! I also note that my Thunderbird version must have updated automatically on opening to the latest version -158. Could this be the problem?