https://help.wpindeed.com/ultimate-membership-pro/

Forum volunteers are also not given access to commercial products, so they would not know why your commercial theme or plugin is not working properly. This is one other reason why volunteers forward you to the commercial product’s vendors. The vendors are responsible for supporting their commercial product.

That being said, they have a support doc which says that the UMP avatar won’t replace the default WP one, so you may need to alter your template (in a child theme).