Plugin Theme Conflict

After installing Ultimate Member I have discovered there is a conflict between UM and a theme used in a template purchased from Template Monster (No 52458).

This conflict goes away if I activate Twenty Fourteen, but returns when I go back to the theme I am using (which can be seen at https://www.cycle2give.com).

Template Monster support said they will fix it, but for a fee of $320, which seems very steep and I have no guarantees there will no be further conflicts with extensions I want to use, with potentially other similar costs involved.

Does anyone have any suggestions? Could this conflict be the result of CSS changes made by Template Monster Support, of which there were many due to issues in optimising the site layout.

Thank you,
John

https://www.ads-software.com/plugins/ultimate-member/