The Washington Post has a piece up that noted some of the reasons for delay. Unfortunately the piece is paywalled so I'll excerpt a relevant portion below.
The piece is at
https://www.washingtonpost.com/business/2020/04/16/coronavirus-cares-stimulus-check/
Excerpt related to the "status unavailable" message:
- You aren’t eligible for a payment.
- Your payment is based on your status as a Social Security, disability or Railroad Retirement beneficiary. In this case, the IRS will use your SSA or RRB Form 1099 payment information. Your payment information isn’t available on the Get My Payment tool.
- You have not filed a 2018 or 2019 federal tax return.
- You filed your 2019 return, but it hasn’t been fully processed.
- You used the non-filers tool, but the information you entered is still being processed.
- There’s a problem verifying your identity when answering the security questions.
There are also a few glitches in the program related to pretty special circumstances.
One is apparently if you neither owed nor were refunded anything on tax returns filed for 2018 and 2019, the program is unhappy. Don't ask how that tripped up their spaghetti code but I guess your perfection was unexpected by the US government? Anyway they're working on it.