dbDelta not installing database

There is error in sql query. You have defined time as datetime and default value mentioned in current_timestamp. Define time as timestamp. Also specify length of email and page fields.

Corrected query:

$sql = "CREATE TABLE " . $table_name . " (
     id INT NOT NULL AUTO_INCREMENT,
     time TIMESTAMP DEFAULT CURRENT_TIMESTAMP NOT NULL, //Change datetime to timestamp
     email VARCHAR(50) NOT NULL, //Change length
     page VARCHAR(50) NOT NULL, //Change length
     UNIQUE KEY  (id)
   ) ". $charset_collate . ";";