Complete log when bundling and publishing:

17:51:43:320 BACKEND (E): Http Error apiCode="ResourceNotFoundError", message="Resource asset not found"
17:51:43:320 BACKEND (E): [RestApi] ID:[4] Error Code:400 - Bad Request, apiCode="ResourceNotFoundError", message="Resource asset not found"
17:51:43:320 BACKEND (E): Error Code:400 - Bad Request, apiCode="ResourceNotFoundError", message="Resource asset not found"
17:51:53:325 DEFAULT : Creating bundle...
17:51:53:348 RESOURCES : ResourceDB: saving cache (id=0 name=Overthrow path=D:\Projects\Arma 4\Overthrow.Arma4/resourceDatabase.rdb)
17:51:53:349 RESOURCES : ResourceDB: cache successfully saved
17:51:53:349 RESOURCES : ResourceDB: saving cache (id=3 name=profile path=C:\Users\Aaron Static\OneDrive\Documents\My Games\ArmaReforger\profile/resourceDatabase.rdb)
17:51:53:350 RESOURCES : ResourceDB: cache successfully saved
17:51:53:350 RESOURCES : Packaging project started.
17:51:53:350 DEFAULT : Compression level: 6
17:51:53:418 DEFAULT : key: 232d61464c060b0e505d020b0b525353
17:51:53:419 RESOURCES : Packaging done. Result: 1
17:51:53:421 RESOURCES : Gproj file copy successful
17:51:53:422 RESOURCES : Project thumbnail copy successful
17:51:53:422 DEFAULT : Created PAK files:
17:51:53:423 RESOURCES : 1: C:/Users/Aaron Static/OneDrive/Documents/My Games/ArmaReforger/publish/Overthrow/Overthrow.pak
17:51:53:432 RESOURCES : Packaging project successful
17:51:53:434 RESOURCES : ResourceDB: saving cache (id=0 name=Overthrow path=C:/Users/Aaron Static/OneDrive/Documents/My Games/ArmaReforger/publish/Overthrow/resourceDatabase.rdb)
17:51:53:435 RESOURCES : ResourceDB: cache successfully saved
17:51:53:456 DEFAULT : Computing MD5 @"C:/Users/Aaron Static/OneDrive/Documents/My Games/ArmaReforger/publish/Overthrow/Overthrow.pak"
17:51:53:517 PROFILING : Computing MD5 took: 60.297900 ms
17:51:53:517 DEFAULT : Computing MD5 @"C:/Users/Aaron Static/OneDrive/Documents/My Games/ArmaReforger/publish/Overthrow/addon.gproj"
17:51:53:518 PROFILING : Computing MD5 took: 1.323000 ms
17:51:53:518 DEFAULT : Computing MD5 @"C:/Users/Aaron Static/OneDrive/Documents/My Games/ArmaReforger/publish/Overthrow/resourceDatabase.rdb"
17:51:53:519 PROFILING : Computing MD5 took: 1.122500 ms
17:51:53:519 DEFAULT : Computing MD5 @"C:/Users/Aaron Static/OneDrive/Documents/My Games/ArmaReforger/publish/Overthrow/thumbnail.png"
17:51:53:523 PROFILING : Computing MD5 took: 3.947100 ms
17:51:53:523 DEFAULT : Computing MD5 @"C:/Users/Aaron Static/OneDrive/Documents/My Games/ArmaReforger/publish/Overthrow/previewImage.jpg"
17:51:53:526 PROFILING : Computing MD5 took: 2.834200 ms
17:51:53:526 DEFAULT : Computing MD5 @"C:/Users/Aaron Static/OneDrive/Documents/My Games/ArmaReforger/publish/Overthrow/screenshot0.jpg"
17:51:53:530 PROFILING : Computing MD5 took: 3.525200 ms
17:51:53:530 DEFAULT : Computing MD5 @"C:/Users/Aaron Static/OneDrive/Documents/My Games/ArmaReforger/publish/Overthrow/screenshot1.jpg"
17:51:53:535 PROFILING : Computing MD5 took: 5.356700 ms
17:51:53:535 DEFAULT : Computing MD5 @"C:/Users/Aaron Static/OneDrive/Documents/My Games/ArmaReforger/publish/Overthrow/screenshot2.jpg"
17:51:53:538 PROFILING : Computing MD5 took: 2.356500 ms
17:51:53:538 DEFAULT : Computing MD5 @"C:/Users/Aaron Static/OneDrive/Documents/My Games/ArmaReforger/publish/Overthrow/screenshot3.jpg"
17:51:53:543 PROFILING : Computing MD5 took: 5.258400 ms
17:51:53:543 DEFAULT : Computing MD5 @"C:/Users/Aaron Static/OneDrive/Documents/My Games/ArmaReforger/publish/Overthrow/screenshot4.jpg"
17:51:53:547 PROFILING : Computing MD5 took: 3.842200 ms
17:51:53:547 DEFAULT : Computing MD5 @"C:/Users/Aaron Static/OneDrive/Documents/My Games/ArmaReforger/publish/Overthrow/scenario_image_0.tif"
17:51:53:562 PROFILING : Computing MD5 took: 14.607400 ms
17:51:53:562 RESOURCES : Saving manifest successful: C:/Users/Aaron Static/OneDrive/Documents/My Games/ArmaReforger/publish/Overthrow/manifest.json
17:51:53:598 DEFAULT : Bundle successfully saved into: C:/Users/Aaron Static/OneDrive/Documents/My Games/ArmaReforger/publish/Overthrow/
17:51:53:605 RESOURCES : Creating bundle successful
17:51:54:872 DEFAULT : Publishing bundle to Workshop...
17:51:54:881 DEFAULT : Validating bundle...
17:51:54:955 DEFAULT (E): Bundle does not meet format requirements
17:51:54:956 DEFAULT (E): Validating bundle failed. Aborting publish.
17:51:54:961 RESOURCES (E): Publishing failed

the brand new project seems to be different now, it actually attempts to publish with a progress bar then shows this error:

DEFAULT (E): Addon processing failed
RESOURCES (E): Publishing failed

but my actual project fails as above

Adding a single conf file to the blank project works, it publishes successfully. But for my actual mod it doesnt work.

You can try for yourself via my github: https://github.com/ArmaOverthrow/Overthrow.Arma4

Disregard.. it now publishes. I replaced the scenario image with a new one from scratch and that fixed it

Adding a single conf file to the blank project works, it publishes successfully. But for my actual mod it doesnt work.
You can try for yourself via my github: https://github.com/ArmaOverthrow/Overthrow.Arma4 basket random

New issue with thumbnails.