I need help getting a hold of support for a plugin

I Purchased the Jevelin theme by Shufflehound from ThemeForest some time ago. The theme comes bundled with the Yellow Pencil plugin, and I’ve been using it to make some design changes, however in the past few days its been buggy and has created problems.
Shufflehound support has not been as helpful as I need them to be so I’ve tried reaching out to Yellow Pencil support directly. However, when I input my purchase code for Jevelin it doesn’t register it as valid and won’t let me submit the ticket.
I don’t know what to do at this point. Please help.

How long ago was ‘some time’?

You don’t get a license or purchase code for bundled plugins https://help.market.envato.com/hc/en-us/articles/213762463-Bundled-Plugins

Assuming the issue falls into support policy then it would be the theme author who would need to help you https://themeforest.net/page/item_support_policy

If you are still within your 6 months (or extended) support period and the author is not responding then you can get in touch with Envato https://help.market.envato.com/hc/en-us/requests/new