Have you performed isolation testing?
This is simply swords and it's dependencies alone. Originally happened in my modpack, isolated it to a single test mod to test for compat issues. Conclusion: bug in Simply Swords itself.

Describe the bug
I've tried both using commands and the radiance Nether Gem ability to gain the Immolation effect, in both scenarios the effect immediately ends within the next 0.5 seconds. Sometimes it ignites enemies, but most of the time it does nothing. This happens even if I use commands to make the effect last a certain amount of time.
This bug exists both in the latest version (1.56.0) and before the Immolation rework in 1.55.0.

To Reproduce
Gain the Immolation effect.

Expected behavior
I expected Immolation to last for the duration of the effect, periodically damaging enemies in the aura until it ends. Instead, it did nothing.

Screenshots
If applicable, add screenshots to help explain your problem.

Additional Info:

• Modloader: Forge
• Modloader Version: Forge 47.4.0
• Minecraft Version: 1.20.1
• Mod Version: 1.56.0 and before
• Environment: Singleplayer

Additional context
The reason I'm certain Immolation is supposed to last the whole duration of the effect instead of ending immediately is because I used this mod in the same modpack but in 1.19.2 (with a few mods removed due to them being outdated) and Immolation worked exactly how I expected it to.

For whatever reason, playing my modpack with all of my mods together, I found that if my offhand is empty, Immolation works as expected, but as soon as I put something in my off hand, Immolation because impossible to retain. This did not work when using Simply Swords alone, however, for some reason Immolation doesn't work at all when Simply Swords is by itself. I'm not sure why.

(edit): not including blocks. Placing a block in my off hand did not prevent Immolation from working properly)