Activating on localhost/xampp

Hopefully someone can help with this.
Posting it here because it’s happening with all PP themes.

Recently gone to make a wordpress site in an xampp local server.

I can make sites, install wordpress, themes, plugins etc. no problems, can essentially do everything offline that I can online with one exception.

When I go to activate any PremiumPress themes I am getting a page show up after hitting “save & continue” with these messages.

Warning: Illegal string offset ‘sidebar-3’ in C:\xampp\htdocs\sma\wp-content\themes\BT\framework\class\class_functions.php on line 372

Warning: Illegal string offset ‘sidebar-3’ in C:\xampp\htdocs\sma\wp-content\themes\BT\framework\class\class_functions.php on line 380

Fatal error: Uncaught Error: Cannot use string offset as an array in C:\xampp\htdocs\sma\wp-content\themes\BT\framework\class\class_functions.php:380 Stack trace: #0 C:\xampp\htdocs\sma\wp-content\themes\BT\framework\class\class_admin.php(838): core_admin_2_themeinstall() #1 C:\xampp\htdocs\sma\wp-includes\class-wp-hook.php(298): wlt_admin->_admin_init(”) #2 C:\xampp\htdocs\sma\wp-includes\class-wp-hook.php(323): WP_Hook->apply_filters(NULL, Array) #3 C:\xampp\htdocs\sma\wp-includes\plugin.php(453): WP_Hook->do_action(Array) #4 C:\xampp\htdocs\sma\wp-admin\admin.php(154): do_action(‘admin_init’) #5 {main} thrown in C:\xampp\htdocs\sma\wp-content\themes\BT\framework\class\class_functions.php on line 380

Not entirely sure what is happening it makes it so I am unable to activate the themes which of course prevents me working on them.

It’s been a while since I’ve done an offline wordpress site, but I’ve been able to activate the PP themes in Xampp before.
Running Xampp as Adminstrator, and have tried all of the PP themes.
Also done different wordpress installs, e.g Bitnami, and standard WP install.

Same result every time regardless.
As far as I am aware everything is set up as it has been in the past when it has worked.

Anyone have any ideas of what is happening and how to fix it?
Got a feeling it will be something simple.