Hi, @RueNel .
I just cleared this issue with the post below.
After upload on 'Upload Fonts' window, it just showed like as if there is no font file selected, however, it was selected.
I clicked save button and was able to apply custom fonts in my logo text using Font Manager.
After upload and selection, it appears like there was no font file selected, but after I press save button, it was added precisely.
So now, I can use Font Manager perfectly.
Thanks a lot for all those staffs who helped me.