jei is installed but is not showing up is single player world. even checked to see if it was hidden and still not showing

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AFAIK hasn't been fixed so shouldn't be stale

Thanks for the report!
I need some more information to solve this issue, please paste your full fml-client-latest.log or latest.log to https://gist.github.com and link it here.

This has been automatically marked as stale because it has not had recent activity, and will be closed if no further activity occurs. If this was overlooked, forgotten, or should remain open for any other reason, please reply here to call attention to it and remove the stale status. Thank you for your contributions.

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Just randomly encountered this issue; it was working fine, and I restart the pack and its not showing. The show/hide button does not show JEI either, and the keybinding menu does not show a button clash.
Issue persists when creating a new world, and when re-entering my current world.
Not sure if its related but this happened immediately following a password reset from Mojang.
JEI 7.6.0.62
Forge 35.1.4 (recommended version on MultiMC)

[also present;
ContentTweaker 1.0.0.develop.9
CraftTweaker 7.0.0.27
Create 0.3
FTB GUI Library 1604.1.1.26
ImmersiveEngineering 4.1.2-129
OpenLoader 8.0.1]

----edit-----
Found the problem, and its sitting in the chair.
I've added a CT recipe using tag:forge:nuggets/platinum when no mod present adds platinum nuggets.
(the lack of platinum did not throw any immediately apparent error on /reload, JEI not showing was the first apparent symptom.)

Same thing happens to myself and everyone else who uses my server. (Debian 10 on a VM)

MC Version: 1.16.5
Modpack: Brass v0.4.0a (modlist: https://www.modpackindex.com/modpack/22520/brass)

Simply relogging into the server fixes it for everyone.

same here, usually it only append on the first time i join a server, logging off and log back in fix it.

Forge 35.0.17
JEI 7.6.0.58

i can second this. it has loaded into forge however there is no jei gui shown, nor can i summon the recipe screen on r or u keys pressed.

Similar issue JEI doesn't appear when joining a server when the pack is first loaded up i've found that joining a singleplayer world and then joining the server fixes it
Edit
leaving and rejoining the server seems to also fix this issue but JEI appears to work first try when joining a singleplayer world
Versions
Minecraft 1.16.3
Forge 34.1.42
JEI 1.16.3-7.6.0.51 (BETA)

not sure if it matters but these were the most recent versions available on the Twitch Launcher at the time of writing this comment 15/11/2020

let me know if you'd prefer this to be commited as it's own issue

same thing happening on my modpack

Same as all of these, the leaving and rejoining without a relog does work though

i too am having this issue on a singleplayer world. i can't relog because an unrelated mod crashes the game.