When a roleplay partner or group goes silent, what should I do? In the past, I've often messaged people about posting, but recently I've been leaving that up to the RPs themselves. "They'll post when they can" was my thought, but instead I've found that RPs die a lot faster now. So, basically, I'm wondering whose responsibility is it to keep the RP going. Is silently waiting something that I should continue to do?

If you're the GM, it's your job to make sure things move forward.

Sadly, most RP goers are relatively poor communicators, and they won't speak up unless personally addressed. If they are waiting on someone to post, going on vacation, etc, chances are they are staying silent. It's also not uncommon for people to ghost or flake. Flakes in particular are a problem because they will constantly tell you that they are going to do something and never will. If you're the GM, you should let everyone know via OOC or discord that you are going to post soon and move everything forward. Sometimes people lose track of time, etc. Don't be angry or belligerent, but staying silent is not the answer.

As for 1x1 RPs, that's something I've had little luck with. But I don't see how speaking up can hurt.

For 1x1 it is quite simple to me. Establish you'd like something once a week and want communication if it will take longer. You now have an 'official' premise before anything begins to poke them after a week. I go further and universally hold that after a few weeks and a couple prods, I shelf the roleplay temporarily and wait the rest of the month. If a full month passes without communication about leaving, I drop them with no regrets whatsoever. If they were just legitimately offline, I might pick it back up if they show up again. If they were frequently online and obviously ignoring me, bonus points for not saying boo while posting elsewhere or straight up looking for another partner, they can fuck off for the rest of their tenure on the site. Had plenty of each occur.

There's a few more conditions, but that's the gist, and in the event it's an announced absence, I'm much more generous with my time table and am completely generous if the given partner just doesn't feel it and tells me so. Key, though, is poking a few times first.

Still expect frequent failure with any higher amount of partners and adjust your expectations to expect very little. Disappointment will not come often for that.

As for group roleplays.

"They'll post when they can" was my thought

oh, ye sweet summer child

Public roleplays have all sorts of factors for failure. One that applies here is a lack of investment and/or obligation, paired with attitudes like "Just another roleplay, fuck it", "dammit I forgot about it", "I don't feel it anymore but I don't wanna say anything". Quite to the contrary of your new approach, double the fuck down. Again establish this in the OOC beforehand. Set reasonable waiting frames and then keep your own little strike system. Keep people talking and obliged. Have an OOC dynamic so people have a reason to come around more regularly, regardless if this is by thread or discord. People who legitimately have busy lives should be pretty clear and can get a wider berth. People who dump egregious amounts of time into other interest checks while flipping yours off and not telling you they really don't care anymore should be booted and worked around.

The gist here is to encourage your active players, poke and motivate your slower players, and trim the ones who constantly fail and lead to the apathy effect resulting from no progress. You are the primary motivator. If you lie down, if the GM doesn't take initiative, failure rate is guaranteed to rise. All of the above depends on circumstance and may not save you in the end regardless, but general views on roleplay success are out of scope right now, so I'll just say taking an active role in keeping participants and partners committed is a essential to going anywhere. I consider a healthy OOC sideline and good chemistry to be pretty nifty too.

1x1 RP partners who are worth waiting around for are the ones who are honest and say if they cant post for a while for whatever reason. Most often people are afraid to hurt the other's feelings if they find the rp isn't working out. 90% of the time the other one wants to make it work so will adapt or work with you to make it enjoyable for both of you. If you cant be honest about how you feel about an rp then the other will never know and are unable to fix it. Just because an rp slows down doesn't mean it cant pick back up, or go through a restart. And it doesn't mean you should give up on a partner's writing either. So when prodding, I ask if there is anything I can do to make it easier/better for them or ask how they are doing in case of irl problems. Some people just forget to tell you what's going on, maybe they don't think we even care as 'faceless' people on the internet. But if they really are just blatantly ignoring you, they aren't worth chasing or even wasting time on.

I always appreciate being told whether someone will be on hiatus or leaving an rp so I can re-open my interest check for new potential writers who are looking for a partner. In the end its just polite to keep communication open. Some people don't realise the amount of time and effort we invest in a story and in that partner, others do. Its just finding the diamonds in the ruff.