I think I understand exactly what the problem is. You are using a "Verify Exists" step inside of the If/else statement and your test fails on that step, because the element cannot be found. The problem is that the "Verify Exists" step performs the verification only once against the cached copy of the DOM tree(it doesn't wait for the element to exists).
One way to overcome this is to add a fixed execution delay step right before the "Verify Exists" step, but we don't recommend this approach.
Another option is to set the EnsureStateIsCurrent property on that step to True(see screenshot). This will refresh the DOM tree before performing the verification, but this still does not guarantee that the verification will succeed.
The best approach in this case is described in this article
from our Troubleshooting Guide. If you change the verification from "Verify Exists" to "Wait For Exists", Test Studio will wait up to the time set in the Timeout property(see screenshot), refreshing the DOM tree on every 500 ms, and when the element is found will proceed with the next step.
the Telerik team