I've developing an update to an existing Laravel System (currently running Laravel 6 and PHP7.4), that runs on both EC2 and Laravel Vapor Setups, and have run into some very strange issues that only present themselves on Vapor Setups. These issues relate to Cookie Generation Failing and POST Routes being ignored when handling Routes.
Issue #1: Cookies No Longer Being Set
The first issue presents itself immediately upon loading the system up for the first time, no cookies are being saved, even though our .env is configured to do so:
SESSION_DRIVER=cookie
Without Cookies being generated, forms can't be processed and users cannot be marked as authenticated.
The system itself has had no changes made to it in areas that would touch core logic around Cookies, but none are now being generated. If we revert the codebase to the previous release without these changes, the system runs perfectly on the Laravel Vapor Setup, but runs without issue using both version of the code on the EC2 Setup.
Potentially Related: Redirecting users seems to be being done with JavaScript on the problematic Vapor Setup, whilst EC2 and Local Development Environments are managing to do so using headers. This indicates there's an issue somewhere in the code that's being used, but the areas that manage that code, as mentioned a few times, haven't been touched during development.
Issue #2: POST Routes Being Ignored
This might be a run on from the first issue above.
POST Routes are being completely ignored from our web.php file. I've tried submitting forms, I've tried using Insomnia to make requests to them, and have even tried setting up a route that would catch requests to any route that was using the POST method, and in each case they were being completely ignored by the system.
Submitting our login forms leads to a strange error being output:
Call to a member function can() on null (View: /var/task/resources/views/core/main/parts/headermenu.blade.php) (View: /var/task/resources/views/core/main/parts/headermenu.blade.php) (View: /var/task/resources/views/core/main/parts/headermenu.blade.php) (View: /var/task/resources/views/core/main/parts/headermenu.blade.php)
This error is strange because it should only be displayed after a user is authenticated, but submitting any details to the system gets this output, even blank details. I'm not sure how the user ends up on an authenticated page, as the POST route that handled authentication is being ignored, so no authentication logic is ever being run. I can, at least, confirm that the system is able to connect to the database to run verification logic, but the route that does so is never accessed because of this issue.
Honestly, I'm coming up blank on solutions to both of these issues, but they're blocking progress with this feature. Any and all guidance on where to look, or how to resolve the above would be most greatly appreciated.