You need look at your Thrash folder, if they aren't there, maybe your Thunderbird are configured to get messages after this date, you can change it going to Edit >> Account Settings >> in the right panel click on Synchronization & Storage and see your configurations about Synchronization dates. Also look at your webmail, maybe the provider deleted your messages.

Still cant get anything further back than Jan2015

Did you try see in the webmail if your messages still are there?

it was helpful but still no further back in time

What email provider? What are the account settings shown in troubleshooting information on the help menu? If the account is IMAP. What ios your mail providers retention settings? Do they auto age and delete mail over say a year old?