User cannot attach a Pdf file when replying an email.

I am working a case where my user cannot attach a Pdf file when replying an email. This is the error the user is getting:  "We can't send this file because Content Deliveries isn't enabled either for you or for your Salesforce organization. Ask your administrator to enable Content Deliveries if you need to send files."

The "solutions" that I have tried but with no results are the followings:

• Salesforce CRM Content is enable in my Org.
• I checked “Autoassign feature licenses to existing and new users” in Salesforce CRM Content but still got the error.
• My users have access to Libraries.
• My users have all access to the Document Object. 

• My user uses Salesforce Lightning (User does not have access to Classic and we do not want to give access only for this matter)
• I tried to send the actual file with my user (Administrator) and was able to attach it.
• I tried to send a different file (a Pdf test file that I created) and I was able to attach it with the user account, but when I tried to attach the file that she needs to send I got the same error.

The file that the user needs to send is 19M, in our setup we got this option enable:

Email Attachments > “Include as attachment up to 3 MB or as links if more.”

Therefore, I tried to Enable 'Create Public Links' from: https://help.salesforce.com/s/articleView?id=000317480&type=1

I searched within the System permission but did not find the one for “'Create Public Link”.

There is a note in that support page that says:

If the content permission is not available, make sure that you have “Autoassign feature licenses to existing and new users” and Salesforce CRM Content enabled first. If it still does not show up, then you may need to Create a Support Case to request Support to enable the Content Delivery setup on your organization. For more information, review Enable ‘Content Deliveries’.

I had checked the “Autoassign feature licenses to existing and new users”, and still couldn’t find the “Create Public Links”.

I am running out of ideas to solve this and we do not want to request the Enable Content Delivery to SFDC support because we understand that it can be solved in another way since with Admin User I was able to attach and send the file. 

Could someone kindly suggest any other solution that I haven't tried? Thank you!