Cannot upload H5P file

I want to upload a new H5P block in Moodle 3.11 running on a local server.

For testing purposed I am working with the greeting-card example from https://h5p.org/node/885 .

When uploading that file, everything works as it should.

When unzipping the file and changing some css, I am no longer able to upload it to my moodle instance:

- I used the command 'h5p pack -r greeting-card-edit' to create a .h5p file which gives me the following error:

Validating h5p package failed. A valid content folder is missing A valid main h5p.json file is missing

 

- I manually zipped up all the files and subfolders in the greeting-card folder and changed the .zip extension to .h5p and get this error

Validating h5p package failed. File "H5P.GreetingCard-1.0/" not allowed. Only files with the following extensions are allowed: json png jpg jpeg gif bmp tif tiff svg eot ttf woff woff2 otf webm mp4 ogg mp3 m4a wav txt pdf rtf doc docx xls xlsx ppt pptx odt ods odp xml csv diff patch swf md textile vtt webvtt js css. File "H5P.GreetingCard-1.0/language/" not allowed. Only files with the following extensions are allowed: json png jpg jpeg gif bmp tif tiff svg eot ttf woff woff2 otf webm mp4 ogg mp3 m4a wav txt pdf rtf doc docx xls xlsx ppt pptx odt ods odp xml csv diff patch swf md textile vtt webvtt js css. File "content/" not allowed. Only files with the following extensions are allowed: json png jpg jpeg gif bmp tif tiff svg eot ttf woff woff2 otf webm mp4 ogg mp3 m4a wav txt pdf rtf doc docx xls xlsx ppt pptx odt ods odp xml csv diff patch swf md textile vtt webvtt.

Any ideas on what I am doing wrong here?