This notification comes up for Etsy users since Facebook and Instagram don't treat etsy.com as a valid website or domain name for your business. Since Etsy is a marketplace and not a unique website, an easy solution to this is that users on Etsy get their domain verified.
Here's Etsy’s support page on setting up a verified domain for Facebook shops: https://help.etsy.com/hc/en-us/articles/360051633874-How-Do-I-Verify-My-Domain-for-Facebook-Shops-?segment=selling
Here’s also a community thread for additional queries: https://community.etsy.com/t5/Technical-Issues/Trouble-verifying-my-domain-for-Facebook-shops/td-p/131250713
Once you have verified your domain, your url will look something like www.yourstorename.etsy.com.
Now, you will be able to use a custom url for your catalog on Socioh. Simply select “Catalog” on the left tab on your Socioh dashboard to create a new catalog.
Then click on the "Create Product Catalog" button, choose all your products in the “Select Products” screen and go to next screen (the "Review and Save" screen).
Here, you’ll get the screen above, where you can save your custom url/domain name.
Remember to check the box to import your product inventory (it is automatically selected), enter your verified domain name, and publish your catalog. You will now be able to connect this catalog to both Facebook page shop and Instagram shopping without the error.
Note: Keep in mind that if you've previously connected a catalog or manually added products to your Facebook Shop, you must remove these to be able to set up correctly. Similarly, if you have a custom domain name you've already added to Instagram, you can use this link to contact Instagram support and submit your new one.
Of course, don’t hesitate to get in touch with us if you continue to face any issues. We’re here to help!