Hi

From console

[14:06:15] [Server thread/INFO]: [DEBUG] Failed to find a seed for Block{mysticalworld:aubergine_crop}[age=7]
[14:06:15] [Server thread/INFO]: [DEBUG] Attempted crop harvest with result FAIL has completed

https://github.com/MysticMods/MysticalWorld/blob/1.14/src/main/java/epicsquid/mysticalworld/blocks/AubergineCropBlock.java

Did you add the seed item to the harvest:seeds tag?

Well its not my mod, so..
Why you making your own tag and not using forge's seed tag?

Because I didn't know Forge had a seed tag, and mine existed before theirs did.

Also, the entire point of tags is that the user can add to them, you can easily add their seed to the tag.