you have not followed the update instructions correctly, specificly:
2) Copy the install/webassist folder and paste it over the webassist folder at the root of your site
3) run the sql script that matches your update path in the install/scripts folder.
make sure to upload the entire install/webassist folder to you site at the root of the power store files.
put another way:
if your site is uploaded to:
there will be a webassist folder at:
you need to overwrite this folder with the one in the install directory of the power store 4.5 zip file.
also in the install/scripts file, run the sql script for your update path on the database, this will create the ps4_countries table.