Can't set certain channels as system messages

So, I made a channel that's supposed to send system messages when someone boosts the server.
At first, I couldn't set it as one, but after about a week, I could so I did. Then suddenly, without anyone tweaking the channel, it became a regular channel (with no system messages). I tried to make it a system channel again, but couldn't. Why so? Any way I could fix it without creating a new one? (The channel is open to view by everyone [even not verified ones], and no one can send a message there)