Yes, you can sign up for a free trial for a guest user again by performing the following actions.
Note that even if you sign up for the free trial again using the same e-mail address used for the previous trial, you will be regarded as a new guest user.

1. Write down the e-mail address of the guest user you want to delete.

2. Click the gear-shaped Settings icon at the upper part of the kintone screen, then select kintone Administration.
   

3. Open Guest Management.

4. Click the Delete icon at the far right of the user you want to delete, then click Delete.

1. Click the Options icon at the upper right of the screen in the guest space to which you want to invite a guest user, then click Manage Guests.

2. Click Invite Guests.

3. In the Guest E-mail Addresses input field, enter the e-mail address you have written down in step 1 of "(1) Delete a Guest Whose Trial Period Has Expired."
   It is also possible to specify a different e-mail address.

4. Enter a comment in the Message input field and click Send.
   The invitation e-mail is sent to the guest user whose e-mail address is specified in the Guest E-mail Addresses input field.