My name is Giada, I am with the Support Team at Shopify!
The issue with the Facebook/Shopify connection still remaining may have to do with a disconnected webhook (from when you did have the Facebook Sales Channel connected to your store) that was either not sent, or not processed properly from when you disconnected Shopify and Facebook. The webhook needs to be resent in order for it to connect properly. We will need you to add the Facebook Sales Channel and reconnect your Facebook Page for this to work. Here are the steps:
1) Login to your Shopify store
2) Click the plus sign beside Sales Channels on the left side
3) Next, to the Facebook Sales Channel click the Add button.
4) Click on the Facebook Sales Channel on the left side and reconnect your account.
After your Facebook Page is connected wait at least a half an hour, we recommend longer than that, from now until morning is a good time. Afterward, disconnect your Facebook Page from Shopify but keep the Facebook Sales Channel connected. The message on your Facebook page should go away after 24 hours. You can then disconnect the Facebook Sales Channel.
The reason for the delay is because Facebook has to get Shopify's job request to remove the shop tab (created by Shopify) from your Facebook Page. Once the shop tab is gone you will be able to follow Facebook's instructions here to add the shop tab back without using Shopify.
If you experience any issues along the way reply to this post and we can assist you further.
Thank you for the update. I have sent you an email so that we can look further into this issue in more detail. We do not have a way of manually disconnecting Shopify and Facebook at this time, but I will be able to find out for certain once we have more information about your store.
Thank you :)
I am having a very similar problem. I am trying to disconnect my Shopify store from my Facebook page, so that I can create just a Facebook shop, but it keeps saying to go to Shopify to manage my collections. I tried the steps you listed above, but it didn't work. Any other ideas?