There are already threads on this topic:
Radeon Prorender for Blender Plugin 2.4 Issues
ProRender plugin crashes blender with tiled rendering
I don't see where anyone is reporting it to AMD as they should: https://www.amd.com/en/support/contact-email-form
Your R9 280X may not be 100% compatible anymore with Prorender as per this General Discussion thread: AMD Stop supporting R9 and Non-Rx Series GPU cards on ProRender
I would open a thread at Blender
EDIT: ProRender Compatibility List has removed the R9 series GPUs as being compatible.
is it possible to get version that compatible with r9?
According to AMD Manager of ProRender Bsavery he was going to make earlier versions of ProRender available at GITHUB: AGAIN - PRORENDER DOESN'T RECOGNIZE GRAPHIC CARD>!>! any help?
Bsavery did upload a link to an earlier version for one R9 User to download so that his GPU will start working again with ProRender but for 3DS MAX.