The first thing to do is to contact Bet365 Customer Support. They may be able to explain reasons why your account is restricted, but they won't necessarily be able to remove the restrictions, depending on why they were implemented.

Even if you have no idea why your account has been restricted, you should still contact customer support to get an idea so you can open it back. And while bet365 customer support can help you discover the reason for your account's restriction, they are not under any obligation to remove the restrictions on it.