Problem with theme management

[zbdblues]

I posted this in 'Themes' but realise this is more suitable here:

No Themes will upload. I'm trying to upload responsive user themes but I can't get any to succeed.

I get error messages, either 400 Bad Request or he following errors were encountered:

• MyBB could not find the theme with the file you uploaded. Please check the file is the correct and is not corrupt.
  

This happens with every theme I've tried to install, so I don't think there's anything wrong with the themes themselves. Any ideas?

MyBB Latest version running on cpanel, manual install.

[HLFadmin]

1. Can you export the Default theme? Save the file after choosing No and Yes for the two options. Edit line 2 in a text editor to change 'name="Default"' to 'name="Test"'
2. Can you import that one? If not, you'll need to look at server side limitations, including upload size limits, if permitted.

Server parameters will be found in the phpinfo dump.

[Ben]

Can you please also verify the CHMOD settings are correct for the directory?