You say you can log in to Tiscali so I'm assuming you have a tiscali.co.uk email address. So let's start with checking that the tiscali mailbox is fully functional.
Select here: Sign in to TalkTalk Mail
Enter your full TalkTalk Mail tiscali email address, select Continue and enter the password, select Sign in.
Select New email and compose and send the same mailbox address a message. Make sure it is copied to the Sent folder and arrives and stays in the Inbox.
If the message didn't arrive in the Inbox then select the main settings cog icon top right. Select the menu item All settings and then Mail in the left pane of the modal that opens. Scroll down to Rules and delete all rules there to make absolutely sure that nothing is diverting mail from your Inbox.
If you found unexpected filter rules then select Security in the left pane and Sign out from all devices. That's to lock out any unauthorised devices. Now scan your email devices for password capturing virus or other malware and upgrade the password.
The Reset password now button in the help article Changing your email password will take you to password reset and recovery.
If the email address is still active on the TalkTalk Mail platform and you have set up password recovery options, in advance, that you recognise from the *****hints, then you can send your alternate email address a link or your mobile a 6-digit code to authorise a password reset.
