I think there is a bug in mac auth. Just link donation with a different mac then relink it back with yours again. Then it will be back working.
First my setup... Mini power pc with intel i5 quad-core processor, 8GB ddr3 ram, Nividia gtx970 gpu, 120GB SSHD, 1TB Hybrid hard drive, using 1Gbit Ethernet hard wired to my router with Cat6 wire with 20Mbit down 8Mbit up internet speed, this is a media mini pc box I built just to run Kodi 15.2 RC2 fast as hell on my big screen, I know its overkill for just media usage, but I like a little future proofing. haha
For me it keeps only happening when I use stalker client pvr in kodi, mac corrupts and I gotta relink. If I just use iptv stalker addon and keep pvr off it doesn't corrupt and all is well.
Haven't played with stb emulator in awhile so I dunno if that is effected. I do keep seeing this effect mag users as well so I'm thinking there is a glitch in the matrix in the mac auth system.
I only run one donation. Only use one device logged in at a time always. Even tried changing macs a few times to different ones from my original with same effect...stalker client pvr works for a few hours, I stop watching and deal with real life, come back later to watch something and I get auth fail, I switch mac on my donation to a slightly different new one, then switch it back to my original one I use, and all works again, but then my mac will auth fail again later, then annoyingly I must repeat relinking my donation over again.
If I just use iptv stalker 9.0.19 addon it never fails. Tested this since I switched from Android tv box to my new mini power pc media setup.
Loving my setup too compared to the Android tv box I was using. This mini pc running kodi 15.2 rc2 makes the sd streams on here look damn near 1080p with the way my nividia card renders upscaling. I'm blown away and now love this service even more, even with minor tech problems NFPS/Rocket are doing a great job fixing them. Hope my testing and this post helps with this relinking bug. I tried to put as much info in as I could. Cheers!