This is not an issue with the WooEnhancer plugin, but with the theme you are using .
They have a typo (or rather, search and replace error) in their code on line 1927.
That line should read:
if ( ! function_exists( 'tgmpa' ) ) {
As they incorrectly changed it, the function is being redefined causing that error.
If you replace that one line in the class-tgm-plugin-activation.php
file within your theme with the line above, WooEnhancer and your theme will play nice together ??
Please also ask the theme author to fix this as this may also cause issues for other users of the theme.
You can tell the theme developers that if they download a fresh copy of TGMPA using the Custom TGMPA Generator, it will serve them with a customized download of TGMPA which will automagically have done the search & replace for them in the correct way.
https://tgmpluginactivation.com/download/
Hope this helps.
Smile,
Juliette