"Block not found" in the checkout editor
In short
The Custom Block shows Block not found when its Block ID setting is empty. Copy the ID from Block Details in Checkout Ninja, paste it into the app block's Block ID setting and save. If the block is blank instead, the ID is wrong or the block is set to Draft.
✓ Applies to
- Advanced and Deluxe plans
- The Custom Block app block in Shopify's checkout editor
✕ Doesn't apply to
- Blocks that show in the editor but not in the live checkout
- The Rules Executor block
Work through these causes in order. They’re sorted from most to least common.
The Block ID setting is empty
This is the only thing that shows the words Block not found. The Custom Block app block was added but no ID was pasted, or the paste didn’t save.
Check: click the Custom Block in the checkout editor and look at its Block ID setting.
Fix:
- In Checkout Ninja, open the block and copy the ID under Block Details.
- In the checkout editor, paste it into Block ID.
- Click Save in the checkout editor.
The Block ID is wrong
A wrong ID doesn’t show an error. The Custom Block just renders nothing.
Check: compare the ID in the editor with the one under Block Details. Look for missing digits and spaces before or after the number.
Fix: copy the ID with the copy button next to it and paste it again. If you deleted the block and made a new one, the new block has a different ID.
The block is set to Draft
A Draft block renders nothing, in the editor preview and in checkout.
Check: open the block in Checkout Ninja and look at Status.
Fix: set Status to Active and click Save. Reload the checkout editor.
The block’s content is hidden by its own settings
The editor preview renders the block the same way checkout does. If none of its visibility conditions match the editor’s preview cart, or every block type in it is Inactive, the preview is empty.
Check: open the block’s Block Visibility card and look at each block type’s Active / Inactive badge.
Fix: test in a real checkout with a cart that meets the conditions, or turn Enable conditional block visibility off while you check placement.
You can’t find Custom Block in the app block list
Check: which page you’re editing. The Custom Block only has positions in the checkout itself. It isn’t offered on the thank-you or order status pages.
Fix: switch the checkout editor to the Checkout page. Open Checkout Editor in Checkout Ninja opens it there directly. Also check that Checkout Ninja is still installed on the store.
On stores not on Shopify Plus, Shopify doesn’t let checkout apps render in the information, shipping and payment steps. Use a development store to test.
Frequently asked
Where do I find the Block ID? +
Open the block in Checkout Blocks. The ID is under Block Details in the right-hand column, with a copy button. It only appears after you save the block for the first time.
Why is the Custom Block empty instead of saying Block not found? +
An ID is pasted in, but it doesn't load an active block. The ID is mistyped, belongs to a deleted block, or the block is set to Draft.
Can I type the block's name instead of the ID? +
No. The Block ID setting only accepts the numeric ID shown under Block Details.