[Lubricant Jam]

I just typed out a lengthy reply however Cloudflare restricted me as apparently I was trying to SQL Inject or a banned word was used (lol).

I'll summarise, it seems like it's 100% your protection and I say this from experience due to being on corero and something like this happening before however it was with VoIP in-game not working/lagging. Essentially, it seems like no A2S_INFO packets are being outputted by your server thus indicating they've got bad rulings. You say it's working after 15 minutes or a restart, this is probably due to a map change triggering an output so that would make sense.

If you know who the protection is posting it here could be an idea as someone else could give you advice on that company and if they've had similar and if you don't know, do a traceroute and figure it out from there. You may be better off contacting your host (that's if they're not a crappy GSP which just resells and has no business relationship with them) and see if they can rectify this.

You know it's not an issue with your server or steam themselves as you say, it's connecting to steam just fine and I can assure you, if your network connection dropped and came back online sometime later, everything would reconnect fine (might have a few issues with some SM plugins crashing due to lost database connection but that's not to do with the server itself).