You added new and/or modified existing poll options after some participants already entered their vote. Doodle would not know what your existing participants would have selected. Therefore it indicates the missing information with question marks. You need to contact your participants and ask them to update their entries, you can read here for more info.
Alternatively, if you manually set the poll options to their original values, the question marks will disappear and the votes reappear. To do this, open the admin-link and click 'Edit'. Change the options to their original values and click 'Finish'. The question marks are gone now.
Hint: If you just want to fix a typo or add some additional information to an option, you might not want to ask your users to update their entries. In this case you can export the poll as a PDF or an Excel sheet before making these changes. Afterwards you can update all the participations with the information you saved before. Simply hover the mouse over the names of your participants to edit their votes