Really Jacob?? This was your cut & paste answer from somewhere else here after 4 years?  You don't even understand the issue that is/was going on here.   Is Cisco giving out points or something for "helpful" post upvotes?  Ridiculous.

Uh... this has nothing to do with the issues everyone is having here... But thanks for your effort!

Downgrading to earlier firmware doesn't solve the issue.  Appears to be the 1-1-2020 credentials expiration bug. https://www.cisco.com/c/en/us/support/docs/security-vpn/public-key-infrastructure-pki/215118-ios-self-signed-certificate-expiration-o.htm...

Spent some time trying to pin this down; tried a few things - formatted flash with clean IOS install (verified SHA to rule out corruption), tried older version... all with same error.  Then I found a thread discussing this same 404 error/issue in reg...

Having the same issue with some 3602i's that I converted to standalone also w/153-3.JF11.   Can access all settings pages through the GUI, but when you change anything apply and click "OK" in the pop-up warning box, it displays "404 not found" in the...