Sometimes after configuration Thank You page may not show up.
Follow these steps one to see if the page appears:
Step 1: Save the page and check if thank you page appears
Step 2: If you have set up certain “Rules” which are not matching the criteria of the order
Step 3: Reset the permalinks and check if thank you page appears
Step 4: Check the global settings and see if the Mode is Sandox or live
Step 5: Check the Order Status settings & see if relevant order statuses ( where thank you page will show up) are selected.