Unable to boot into windows after partitioning macOS

Hello all,

I know there are a lot of threads already about this and none of them helped me so I will create a new thread.

Today I wanted to create a new partition on the SSD that windows would be able to read for extra files etc. I resized the partition of the mac. Now I try and boot to windows and it doesn't want to boot. It first didn't show me the option to boot to windows at all when holding down 'alt' at start up, but thanks to this thread: https://discussions.apple.com/thread/6465316?answerId=26354134022#26354134022 that option came back after entering some commands. However, I still cannot boot into windows. When I select windows while booting it gives me a blinking box in the top left corner, but it doesn't do anything after that.

Anyone knows why this is happening and how I can fix it?

Thanks in advance,

Vincent