Cannot add payment methods

[lmcc]

Virtuemart 3.6.10
Joomla 3.9.16
Php 7.4.3

Virtuemart is not allowing me to add any payment method. I have tried several and get the same error:
"Cannot use "parent" when current class scope has no parent in.....  /administrator/components/com_virtuemart/helpers/shopfunctions.php on line 370"

I have reinstalled virtuemart twice, as well as the AIO.

[GJC Web Design]

try php 7.3

[lmcc]

Thank you. I did try php 7.3. I tried that and then rolled back to 7.1. Was not able to add payments with any php 7 version.

[GJC Web Design]

you need to further trace this error .. 

use full Joomla debug and u should get the full trace

[lmcc]

Thank you GJC Web Design. 
I realized after I said I had "reinstalled" virtuemart, that I had not done a full removal before installing again. After doing a clean uninstall of everything (including database tables) and starting over, adding payment methods works fine with PHP 7.4.
I made the mistake of "jumping in" without reading thoroughly first. The error likely resulted from improper installation at the beginning.
Thank you to all who are working to make this a great extension!