Commonly there is something ‘over’ your buttons (or other interactive elements) with visibility setting as Visible, blocking your button click. Could be a number of reasons.
Could also be that you don’t have your mouse enabled properly (mouse & UI mode)
Re-Test in-editor using ‘Standalone’ and ‘New Editor Window (PIE)’ modes, viewport can sometimes do weird scaling of other invisible widgets that can overlap.
Play in viewport and use the widget reflector (Tools → Debug → Widget Reflect) and mouse over the button to make sure there’s nothing else blocking.
Let us know what the feedback is from the above