This issue occurs when the configuration file is not found in your config folder. I give you some steps to solve this problem.
Theme configuration Issue
Step 1. PLEASE GO TO THIS PATH folder_ps/themes/selectyour theme/config/theme.yml
Step 2. check the theme name on the folder
Step 1. PLEASE GO TO THIS PATH folder _ps/themes/selectyour theme/config/theme.yml
>> Please go to this path and check config.yml file exist or not and please be noted file name must be in the lowercase letter.
Step 2. Check theme name on the folder.
>> Check the folder name and then go the inside of the theme folder _ps/themes/selectyour theme/config/theme. yml and open the theme. yml file and find the