Send activities to my students

Read the help section, please, everything is clearly explained there. You need to assign the workbook to your students, then you can open it and move your cursor over a page to select the option "assign as homework".

Rosana, Is it they can't access their workbooks or they are not notified? @JJ, I think student notification is not working well.

Yes, my students are also complaining they are not notified about new homework, but this seems to be a worse problem if Rosana's students can't even access their workbook activities. Rosana, can you give us more details, please? Have you used workbooks before? Have your students? Can't your students access the workbook, or just the new pages on it? Have they done other pages in that workbook? etc.