ServiceNow Submit Button was not appearing on portal catalog item

I found this post useful:

https://www.servicenow.com/community/developer-forum/no-submit-button-in-catalog-item-view/m-p/1823356

steps:

1) Go to Maintain Items i,e the Catalog Item Table for your particular Catalog Item

2) Please pull these columns from the personalized gear 

No Cart, No Order, No order Now, No Proceed to checkout

3) Make sure all these are False.

Check if this resolves your problem.