When you update your theme, depending on how big of a change it is your TikShop feeds may or may not be effected.
As a rule of thumb, if you encounter issues when updating, simply check what page your feed is assigned to in the TikShop admin. Then, make sure the TikShop app block is shown on that page (for non-OS 2.0 themes you'll have to add a code block).
When you publish a new theme your theme
Unless you are updating from a non-OS 2.0 Theme to an OS 2.0 Theme (see below), your feeds will continue to be assigned to the templates they were assigned to as long as those templates still exist with the same name in the new theme that has been published.
If the templates do not exist, your feeds will no longer be assigned to any page templates. Go to the TikShop admin and reassign feeds to the templates you would like them to display on. Then, add the TikShop App Block to the page through your theme customizer and your feed will display on the new theme.
Updating from a non-OS 2.0 Theme to an OS 2.0 Theme
When you update to an OS 2.0 Theme, your feed(s) will no longer be assigned to any page templates. You will have to reassign your feed(s) to templates and add the TikShop App Block to the pages you want the feeds to display on.
As always, should you need any help, feel free to reach out to our support team :)