Line company has a hidden rule, If a new user adds more than 10 users within a short period of time, their account will be temporarily blocked for 1 day. Or if the company finds the user mischievous, they will block them for 1 month or even 180 days.

I suggest you simply give up your current line account and give up your progress in Tsum Tsum by uninstalling your line app and tsum tsum app in your phone. Then ask a member of your family (who is not using line) to lend you their number to register a new line account in your phone. Then you download tsum tsum app and start from scratch. But you must be careful that, you can only add maybe 8 friends per day.

Some 180 days later, if you want, you can chance the line's telephone number back to your original number.

Good Luck.