Error when adding Contact: No default contact folder for account 'one of my POP3 accounts' could be determined

But if I check Accounts / Default Folders / Contacts
when eM Client starts up it says “Local Folders/Contacts/”

After trying to add a contact this setting is cleared …

(I am right clicking an email address in the email view and choosing “Add Contact”)

you should be able to add contact even if you do not have set default contact folder. Right click the contact you want to save and choose Save as. New window will appear where you can select a folder to save contact.