If the Comments App does not show up when you open your website on a mobile browser, there are two possible solutions to fix it:
1. Go to Wix Editor, switch to the mobile view, go to Hidden Elements, and enable the app there.
Here's the Wix Support article for more info about this - https://support.wix.com/en/article/viewing-hidden-elements-in-the-mobile-editor
2. Check if the Wix feature called "AMP" is turned on. Basically, AMP disables all the interactive content, including the Comments app. Disable this feature for the Comments app to work properly.
Here's some information about this feature - https://support.wix.com/en/article/turning-on-google-amp-in-the-wix-blog
Always save the changes you made in your Wix Editor and publish your website for the changes to take effect on your website.