Interestingly enough, there's two accounts: Agent96 and AgenT96 (note the capital T)
[08:10] <&George_> !regdate Agent96
[08:10] <Sonium> Agent96 registered on April 2nd, 2016.
[08:09] <&George_> !regdate AgenT96
[08:09] <Sonium> AgenT96 registered on January 1st, 2016.
[08:12] <&George_> !players Agent96
[08:12] <%Nuwani> Agent96 has been online for 29 minutes. The player has killed 6 people so far, and has died 4 times themself, which makes a ratio of 1.50. Agent96 is a player on Las Venturas Playground, and was last ingame at 2016-04-10 01:07:00. -
http://profile.sa-mp.nl/Agent96
[08:13] <&George_> !players AgenT96
[08:13] <%Nuwani> AgenT96 has been online for 60 hours and 14 minutes. The player has killed 644 people so far, and has died 529 times themself, which makes a ratio of 1.22. AgenT96 is a player on Las Venturas Playground, and was last ingame at 2016-04-09 07:56:01. -
http://profile.sa-mp.nl/AgenT96
I've renamed Agent96 to Agent96_bak, please try joining the server with AgenT96 and you should find that everything is normal again.
