The message clearly says “File Extension should not be greater then 3 character” while the file you have uploaded has the name ‘html’ which is total of 4 character. On Bolt your file name extension has to be a maximum of 3 characters. In this case you will have to change the file name to HTML.
The message clearly says “File name should be less then 10 character.” Your file name has a total of 11 character. Do not forget to count the full stop (.) in the character length. Please change the file name to something shorter like test.htm and it will work.