Curiously though, the key I altered worked for me.
When a new key is created in the registry, a default value name/data is added to it automatically which is usually unused.
...worked for me. How would that be?
Some[thing | one] has fixed the actual problem for you elsewhere.
As you couldn't even open an .eap locally by double clicking, your problem was not solely because of the database server being down. It could be your network that had issues and EA couldn't access the license details from the key store.
OTOH, Sparx has previously confirmed an issue where if the default project is not accessible, EA cannot be launched. However, in this case EA could be launched by double clicking on an .eap