Help with automating new date every month after task is done

I am having trouble getting this automation to work. It’s almost there!

I have a monthly task list, and after I complete the task for the month, I want it to re-appear with the new due date.

Example: “Give dog her medicine on 10/1/2021”. Frequency = 30 days. Once task is complete, add new task for “Give dog her medicine on 11/1/2021”.

I have everything working except the date. Can anyone help? I’ve recorded what I’m doing so you can see. It says “Could not convert string to date.” but I cannot get it to work. Thank you!

Can you please show me the fields “Due” and “Frequecy (Days)” look like? Are the a date field and a number field?

@Per_Carlen Yes, Due = date and Frequency = #