Your account at Galaxy Main https://usegalaxy.org looks to be Ok now (under quota).
You were probably over quota, and purging (permanently deleting) histories/datasets then (optionally) logging out/back into Galaxy reset the quota. When you are over quota, freeing up space is the way forward. This advice will apply to most Galaxy servers with a quota implemented unless it was set up with a custom configuration.
Thanks! Jen, Galaxy team