Residence pvp problem

[TheLondiux]

I made a pvp arena and I protected it with residence, then I activated the pvp, but several players reported that they could not fight. Residence tells me that the pvp is activated but we can not fight. Please help, it's urgent!

 

[TheLondiux]

I fixed the problem.

 

[CreeperFace]

I fixed the problem.

What was it? and How did you fix it? was that a plugin fault?