Turns out that I didn't have much disk space.

Saw this in the FA search logs:

{"type": "server", "timestamp": "2020-06-10T14:34:28,378Z", "level": "WARN", "component": "o.e.c.r.a.DiskThresholdMonitor", "cluster.name": "FusionAuth", "node.name": "ubuntu-xenial", "message": "flood stage disk watermark [95%] exceeded on [NE_DhFssRru-H5oIiLwBjA][ubuntu-xenial][/usr/local/fusionauth/data/search/esv6/nodes/0] free: 887.9mb[4.4%], all indices on this node will be marked read-only", "cluster.uuid": "LGdaij30RrS4FZbgsT_6KA", "node.id": "NE_DhFssRru-H5oIiLwBjA" }

Deleting some things from my hard drive lowered my disk usage below 95% and I no longer saw the message.