There could be multiple causes for this issue, but the most common is that your customer doesn’t have an active discount rule tag on their account or has an incorrect discount rule tag on their account.
Please be sure that this customer has a discount rule tag on their account that will trigger a discount and always triple check that the tag matches the tag you created in Wholesale Gorilla exactly. If you notice that the tags are mismatching between the two areas in anyway, please adjust one of the settings so that they're both perfectly matching.
If your tag situation is in order and matches exactly, you'll next want to triple check that the customer is indeed logging in. Shopify will auto-log out customers after a very short period of inactivity, and browser/device settings can also execute auto-log out functions within varying amounts of time. Please try having the customer log in once more and double check the area where retail prices were displayed, that way you can ensure that it wasn't simply a case of not being logged in correctly.
Finally, if these elements both appear to be in order but the pricing is still not changing, please contact our support team with your Shopify URL (https://xxxxxxxxxx.myshopify.com), the name/email on file of your customer(s) experiencing the issue and a couple of listing examples that this is occurring on so that we may sort it out.