You may want to try clearing your browser's cache and delete the cookies stored on your computer as this can keep TurboTax from functioning properly.  Please see the below FAQ's for instructions:

Delete cookies: https://ttlc.intuit.com/community/troubleshooting/help/how-do-i-delete-cookies/00/25978

Clear cache: https:// ttlc.intuit.com/community/troubleshooting/help/how-to-clear-your-cache/00/26135 

For additional information on accessing and printing your 2018 tax return as a PDF, please see the following FAQ:

https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/00/270...

Why is my PDF downloading as a .txt file in Microsoft Edge?

If you're using TurboTax Online, you may experience Microsoft Edge saving the PDF version of your tax file as a .txt file.

Solution

There are two ways to solve this issue:

1. Change your browser (to Google Chrome or Firefox, for example) and save from there.
2. Replace the .txt extension with .pdf.