Same situation here. I have sent my marriage certificate via webform in December and didn't get any confirmation email. I raised another webform for follow-up in mid-January and the agent confirmed the file is received by the responsible officer. Don't worry, they will add your files to your application even though they don't send a confirmation.
This is what they've told me:
Thank you for contacting Immigration, Refugees and Citizenship Canada (IRCC).
Congratulations on your marriage!
Due to COVID-19, IRCC is experiencing processing delays and we can't give accurate
processing times for most types of applications. We're currently prioritizing applications from people who are exempt from travel restrictions.
We understand that this may be a difficult time for you and we are here to assist you by providing you with the information we have available at this time.
If you've already applied, we invite you to visit our website to
check your application status. Client Support Centre agents cannot give you more information than what is already in your online account or in the Client Application Status tool.
If your application is complex, it may take us longer to process it. It will also take longer to process an application if we need you to submit extra documents.
Rest assured that we are making all the necessary efforts to finalize your application as soon as possible, and that you will be informed when a decision is reached or if additional information is needed.
IRCC is working on giving you the most updated information as the situation evolves, and all our efforts are dedicated to answering your concerns. Our website is updated regularly as more information is made available.
Given these circumstances, we invite you to continue visiting our
website regularly to receive up-to-date information as new announcements are made and to obtain information on travel restrictions and changes to our services that may affect you.
We also verified the information on file and are pleased to confirm that the marriage certificate was received by the responsible office.