My RoKu LT will not up date Prime video version 5.20
That device is no longer supported by Amazon. There's no way to update its Amazon Prime version. You should have received an email about it. You will need a new device if you want to continue watching Amazon Prime with a Roku device. You can check to see if you're offered a discounted device at:
https://my.roku.com/upgrade/prime-exclusive-upgrade/details
https://my.roku.com/upgrade/offers
Many stores are also offering cheap devices this time of the year.
Thanks for the post.
As @renojim mentioned, the Roku LT is a much older device that is no longer supported. However, we would be happy to see what we can do to help get you back up and running.
Please provide us with the serial number of your Roku device (printed on the side/back of the device) and I'll have our support team reach out directly to assist you further.
Thanks,
Danny