Can you help? I Cannot add a new user ,please advise ?

Welcome to the Community, giovanna1.

I'm here to help add a new user in QuickBooks Online.

You'll have to log in as a Master administrator or Company administrator to be able to add a user.

Once done, follow the steps below:

1. Choose the Gear icon at the top, then select Manage Users.
2. Click the Add user button on the right.
3. Select which type of user you'd like them to be.
4. Enter the new user's e-mail address and name.
5. Click Save.

Here's an article for more detailed steps: How to add, delete, or change a user's access.

If you opt to give us a call, check out this steps for our contact information:

1. Select the Help icon in the upper right of the screen.
2. Choose Contact us on the pop-up. 
3. Enter a topic in the How can we help? field (ex. support) and choose Continue. 
4. Click Get our phone number.
5. Enter your contact information.
6. Click Call me.

The information above should help you get pointed in the right direction.

 I'd like to make sure that you're able to resolve this concern, so please let me know how it goes by posting a comment below. Best regards.

It's nice to have you here in the Community, @Christina2020.

Allow me to share with you some information on how you'd be able to add a user in your QuickBooks Online (QBO) account.

First off, let's check if your type of subscription qualifies you to add an additional user.

If you're currently using QBO Simple Start, you can only have one user for Master admin access alone. However, if you're using QBO Essentials, you're able to have up to 3 users which include the Master admin, Company admin, Standard, Time Tracking only, and Take payments only. Lastly, you can have up to 5 users for QBO Plus and up to 25 users for QBO Advanced.

You can check out this article to learn more about this including the different user types and the levels of access in QuickBooks Online: What are the number of users per level of QBO subscription?.

Also, you'll have to make sure you're the Master admin or Company admin of the account to be able to add a user as pointed out by my colleague @ PreciousB.

Once you're able to verify it, you can now add a user's access depending on the type of QBO plan you have by following the steps suggested by my colleague above.

I'll be adding this article in case you wish to delete or change a user in your QuickBooks Online account: How do I delete or change a user in my QBO account?.

As always, you can get back here in the Community if you have more questions about adding a user in QBO. I'll be here to lend a helping hand. Stay safe and have a great day, @Christina2020.