I agree with DeadEyeLefty...... too much pressure pushes the edge into the strop and creates that obtuse angle. The correct amount of pressure with the edge at too obtuse an angle creates the same result: dull edge.
Maybe try very light pressure, no more than the weight of the blade. Find the correct angle by laying the blade on the strop, lifting ever so slightly as you pull the edge into the strop, and stopping just where the edge begins to grab. Maintain this angle and lightly strop the edge toward the end. When you reach the end of the stroke, STOP, lift the blade clear of the strop, reverse and lay the blade flat, find the edge, and strop the other side. STOP at the end of each stroke and lift the blade.
Light pressure. Correct angle. Stop at end of stroke.
Good luck.