Welcome to Track123! When you install Track123, a tracking page is automatically created for you. The link format for this tracking page is 'yourstorename.com/apps/track123'.
If you choose to modify this tracking link, then you need to make sure that you also modify the App Proxy URL as well. Because not synchronizing the URLs would result to an error.
To make sure that everything is modified, then go to TRACK123 > Tracking Page and then click on the three-dot icon and Edit URL.
On the first step, choose which URL you want and just add track or any word you want on the second box.
Then, on the second step, click on the View in Shopify Setting.
Wait for you to be redirected to the page where you can change the App Proxy's URL.
Please make sure that you choose the same URL and word you entered on step 1.
Make sure to SAVE the URL for both the app and the App Proxy URL.
To make sure that you have synced both URL's, you can repeat the steps and check if it shows the same link.
If you have checked and made sure that the links are synchronized, but the tracking link still shows an error, then please be sure to update your menu's setting as well.
To check that, just go to Online Store > Content. Then open the menu that has your Tracking Page.
Click on Edit beside your Tracking Page plug-in and just add the last two parts of your new tracking link.
Click on SAVE, and refresh the page after. Wait for a minute or two for the system fully configure.
If you have followed all the steps that was provided and you still have the same error, then please reach out to our customer support.