The controller basically looks like this

Please don't show us what the code basically looks like in pseudo code. Show the actual broken code.

So I moved back up to the update method and tried to log what was happening inside that if(method is POST) block and got nothing logged there either.

Did you ensure that whatever you're calling when you refer to method is POST is actually returning something? Are you actually calling the proper method to check if it's 'POST'? We don't know, because all you've got is pseudo code.

Did you actually check whether the update() function is being called?

A 404 is page not found. Do you have a route set up to handle the request? It sounds like that may be your problem. In Dancer2, you can specify a route type when defining a route:

any ['get', 'post'] => '/' => sub {

...

post '/garage_update' => sub {
[download]

...etc. If a 'get' request comes in for /garage_update, it'll fail. The / route accepts both GET and POST. I don't know if Catalyst does things like this though.