There are several possible reasons for this problem that may cause your 1688 account to be unable to be activated:

1. Entering the wrong verification code: Make sure you enter the verification code in the activation email correctly. The verification code is case-sensitive, so make sure to enter it accurately.

2. Account frozen: If your account has violated regulations, it may be frozen. In this case, you need to contact the 1688 customer service team to resolve the issue.

3. The activation link has expired: The activation link usually expires after a certain period of time. If the activation email you received was sent a long time ago, the link may have expired. You can try to request the activation email again.

4. The email is identified as spam: Sometimes, the activation email may be mistakenly identified as spam by your email provider and placed in the spam folder. Please check if there is an activation email in your spam folder.

If you have tried the above solutions and still cannot activate your account, it is recommended that you contact the 1688 customer service team for further help and support.