matrix-appservice-slack: Appservice won't create slackbot user

I’m trying to run this appservice on my own instance. I’m following the readme’s instructions. The readme seems inadequate because of #86. Following the readme, when it comes time to invite the slackbot to my admin control room, I find out that the slackbot user doesn’t exist, which means the appservice isn’t creating it.

When I launch the appservice, its console output looks like this:

$ node app.js -c config.yaml -p 25566
Unable to load crypto module: crypto will be disabled: Error: global.Olm is not defined
Mar-24 06:58:53.836 INFO app Matrix-side listening on port %s 25566
Mar-24 06:58:53.850 INFO SlackHookHandler Slack-side listening on port 9898 over http
Mar-24 06:58:53.907 INFO Main Loading teams.db

I don’t know if it’s supposed to progress beyond “Main Loading teams.db”, but it never does. I’ve left it running for days, and this is still the last thing it’s spat out. It might be hanging on something. I have restarted both the appservice and synapse several times to no avail. Anyway, I found out that if I invite the nonexistent MXID to a room despite it not existing, the appservice spits out this line on the console:

Mar-24 06:59:12.936 INFO bridge ::1 - - [24/Mar/2019:06:59:12 +0000] "PUT /transactions/5?access_token=<REDACTED> HTTP/1.1" 200 55 "-" "Synapse/0.99.2"

Sidenote: This seems like the sort of problem that could have been solved just by talking to somebody. So two and a half weeks ago, I went into #bridges:matrix.org (I was told that’s /the/ place to get help with matrix-appservice-slack). Two and a half weeks ago, I asked. No response. A week later, I ask again, no response. Half a week ago, I asked for the third time, and still nobody has acknowledged me. I’m saying this because I feel awkward even posting this in the issue tracker… I just don’t want to keep asking the same question for months, I want to get this bridge set up.