Add Explanation on Why Transaction is Rejected

[iamhsk]

Users are told that their transactions are rejected but don't know why they were rejected. For better UX, we should add some description to explain why it was rejected

0.5 day spike to see where in the code the tx rejection logic lives and investigate why we tell users tx is rejected. If it's not clear on the code and we need to investigate further, then defer this issue to later.