You can change the Client ID or Client secret Merchant Sheets uses for a store at any time. Updating them keeps the store's data, sync history, and history start date, and the store doesn't count again toward your plan.
When to update your credentials
Someone who had your Client secret no longer works with you
The secret may have been shared somewhere it shouldn't have been
You created a new Merchant Sheets app for the store
Data Connectors shows Shopify rejected the keys
Rotate the Client secret
Shopify lets you create a new secret while the old one keeps working, so syncing doesn't stop while you switch.
In your Shopify Dev Dashboard, select Apps, then your Merchant Sheets app.
Select Settings.
In Credentials, select Rotate next to the client secret, then Generate new secret.
Copy the new secret, labeled New. Leave the old one active for now.
Update the store in Merchant Sheets
In the web app, go to Data Connectors.
Under Connect another store or update keys, enter the store's .myshopify.com address in Store URL.
Enter the Client ID and the new Client Secret. The Client ID stays the same when you rotate a secret.
Select Connect. Merchant Sheets saves the new keys and starts a sync with them.
Wait until Data Connectors shows the sync finished without errors.
Revoke the old secret
Once the sync works with the new secret, go back to Credentials in the Dev Dashboard and revoke the old secret. Revoking it before Merchant Sheets has the new one stops your syncs until you update the keys.
Switch to a new app
If you created a new Merchant Sheets app for the store, install it on the store first, following Connect your Shopify store. Then update the store in Merchant Sheets with the new app's Client ID and Client secret, using the same steps. Once the sync works, delete the old app in your Dev Dashboard.