I had the same Problem. Looking into the the client log revealed over 1500 model loading errors for harvestcraft and many "Item json isn't found for 'harvestcraft:#inventory', trying to load the variant from the blockstate json" warnings.
Repackaging the mod jar file helped in my case:
- renamed "Pam's HarvestCraft 1.8.9e.jar" to "Pam's HarvestCraft 1.8.9e.zip"
- unzipped it (7zip or other progam)
- rezipped the content again (so that assets, com, META-INF, and mcmod.info are at the root of the zip file)
- renamed the new zip file back to "Pam's HarvestCraft 1.8.9e.jar
I don't know exactly why that helped, but it seems like minecraft forge couldn't find the model files, even when they were at the correct location in the jar.
The only differences I've seen were that
- folders were 'deflated' before repackaging. Now they are 'stored', and
- the "assets/assets/harvestcraft/models/item" folder changed its CRC from 603138FC to 223B30A9.
I had tried this and it did not work for me. I even removed all the other mods I had and it still has the issue. I am running HarvestCraft 1.8.9e, Minecraft 1.8.9, and Forge 1.8.9-18.104.22.1682.