Hi @Giovanna Salinas ,
First of all, please make sure you have successfully installed the intermediate certificate to your Exchange Server 2016, detailed steps you can refer to: Exchange Server 2016: Install a certificate | SSL Certificates
Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information._
Then you can use below powershell cmdlet to renew your certificate, detailed steps please refer to: Renew an Exchange Server certificate | Microsoft Learn
Get-ExchangeCertificate -Thumbprint <Thumbprint> | New-ExchangeCertificate [-Force]
If you don't know how to open the Exchange Management Shell in your on-premises Exchange organization, see Open the Exchange Management Shell | Microsoft Learn
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