Glad to have you here on the Community page, @roseba.
To give you the right amount of information, may I know what error or problem you're having when trying to print a deposit slip? If the preview screen won't display, this might be caused by a pop-up blocker. For now, make sure that the pop-up blocker option is enabled. Depending on the browser you're using, follow the detailed instructions provided in these articles:
Once completed, try printing the deposit slip again. For additional reference about setting up and printing deposit slips, read this article: Set up and print deposit slips.
Also, I encourage checking these articles for additional reference about printing issues in QuickBooks Online, check out these articles:
Let me know if you have any other questions. I'm always here to help. Have a good day!