They fell out of compliance by not filing the 10k on time. The plan to get into compliance was due by end of grace period and was either not received by Nasdaq by deadline, or was deemed unacceptable. That led to the delisting notice as the grace period expired without an acceptable plan to comply (file the 10k).
Filing the 10k requires hiring a new auditor. Hiring a new auditor likely requires a forensic audit engagement and a comprehensive schedule for completion. Hiring a credible CFO may also be required before a competant auditor would sign an engagement letter. All of this requires some ability to overcome the "lack of reliance on management reps" which may be the biggest obstacle to a new auditor being engaged.
It's not surprising that progress on all of this wasn't sufficient by the deadline. How much progress, if any, is all speculation. Good to see though that they are appealing which will should buy them some additional time.
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