[@netweb Keymaster 8 years, 6 months ago]

I’ve just created the user testtest on the site

I can login successfully using the following 3 methods:
• Using Chrome on my desktop
• Using Chrome emulating an iPhone 7+
• Using my iPhone 7+ directly

Using the above 3 methods worked successfully logging in at *both* these URLs:
• http://www.getswing.co.uk/wp-login.php
• http://www.getswing.co.uk/forums/

The only other things I can suggest is checking with your webhosting if you have any firewall applications or rules that might be the cause of this.

p.s Feel free to the delete the testtest account I created