ANSWER
I believe someone else said it in here but, because the weapons we have do NOT have any glows yet, there is nothing to activate. Hence when you deactivate it, there is nothing there to activate, so when your weapon does get a glow, you can then activate it. I believe everything is working as intended.
This worked for me
Just upgrade your weapon and it comes back. It worked for me… and don’t disabled next time.
its not a bug, until honing lv 10 your weapons doesnt have any effect. Once lv 10 and so on u can again enable/disable your weapon effect! hope it helps!
Same issue here hello Lost Ark staff is anyone reading these threads?
Same this sucks…
The bug is that the icon is clickable before having a +10 weapon…which is the cause a lot of confusion.
this also worked for me thank you!
Oh, ty very much!!
<3
I have just joined the club
No idea, works fine for me ever since I got any weapon to +10 and it actually started having the damned glow to begin with.
Respect dude 
I am joining the club of curious clowns, any fix for the problem yet?
Same problem here.
Guessin’ there isn’t a solution yet… SMH i am too part of this Village of pressing the “Don’t press red button”
Read the entire thread to understand then try this : Weapon effect activate/deactivate bug - #157 by Azure
Bump, same issue.
BUMP
same bug for me. I can’t activate it anymore.
Same issue here 
Might not be a solution for you guys but I personally was just dumb. Effects are only there from weapon lvl 10 (green effect). So as soon as you step a tier up from T1 to T2 or T3 and your weapon is back to lvl 5, you effect is gone until you level your wepon up again to 10. Once you reach tier 10 the effect will be back (can switch it back on and off).