MINECRAFT VERSION: 1.15.2
FORGE VERSION: forge-1.15.2-31.2.30
REALISTIC TORCHES VERSION: RealisticTorches-1.15.2-3.0.0

HOW TO REPRODUCE THE ISSUE

• In vanilla 1.15.2, start a new save (can be in creative mode)
• Save and exit the save and quit minecraft
• Install forge and place this mod in the mods folder
• Open up minecraft and play the previous save
• Try to craft a vanilla torch by using the Glowstone Crystal: it won't work (all other crafting recipes work)
• Save and exit that save
• With forge and the mod installed, start a new save
• Try to craft a vanilla torch by using a Glowstone Crystal: it should work properly now

What do I expect?
I expect to be able to craft realistic torches properly no matter if i'm starting a new save file with forge and the mod installed, or if i'm resuming a previously saved game from before installing the mod.