TalkTalk have been posting messages that they had webmail problems, and they are working on it. Whether this is the reason you are having problems, you might need to wait and see.
I use TalkTalk and have had some webmail problems, with some emails not opening correctly.
You could try and alternative route to your TalkTalk email. If you try this, then on the opening page of the link, there is an option regarding security, choose the highest possible for best protection. You will also need to use your TalkTalk webmail password, but that should be secure. This is the link you could try click here