I believe itch io does not accept copy and paste. You should save a png file and then upload it to the itch io post.
By the screenshot, the error seems that the value passed into the meta tag HpCost is not a string. But I can't seem to find a reason for that. I believe I will need a sample project from you replicating the error so I can take a look and see what the problem is. I tested it here and it worked just fine.