Unable to delete third party application iOS 18.4

An App Developer won't be able to help you with App deletion.

Assuming that the iPad is not centrally managed by a School or other Educational establishment, start here:

Delete apps on your iPhone, iPad, and iPod touch - Apple Support

Assuming that your iPad is not centrally managed by an Educational Establishment or Business (as the device may be remotely managed) - if you are experiencing difficulties with adding, updating or removing Apps from your iPad, you’ll need to check your ScreenTime restrictions:

• Settings > Screen Time > Content & Privacy Restrictions > iTunes & App Store Purchases > Adding Apps - set to Allow
• Settings > Screen Time > Content & Privacy Restrictions > iTunes & App Store Purchases > Deleting Apps - set to Allow
• Settings > Screen Time > Content & Privacy Restrictions > iTunes & App Store Purchases > In-app Purchases - set to Allow

Be aware that Apps can be removed from Home Screens without actually deleting the App from the device. In such circumstances, the App can be located and deleted from the App Library.

Find and use your apps in App Library on iPad - Apple Support

Have you considered a 'Reset' of your device?

Restore your iPhone, iPad or iPod to factory settings using a computer – Apple Support (UK)

Please post a screenshot of the window… edit ou any personal info if displayed.

You need to contact the app developer..l Apple is not going to contact them.