I solve the problem, and it worked with me!.
This error happens when the City textbox is not filled in the full address of the account.
How to solve it:
I am unable to submit proposals - Keep getting the following message - To submit a proposal, update your address. I have updated all my details and also upgraded my membership plan to Plus. Upwork has also made my profile public.
Thanks for reaching out to us. I checked and it seems that you do have an address on your account. However, you haven't selected a membership plan. To do so, please go to your Settings > Membership & Connects and from that page select your desired membership plan and you should be able to submit proposals afterward. Please let us know if you continue experiencing this issue so that we can assist you further.
You will need to add your city as well in the filed "City" so that you`re able to submit proposals. To do this please go to Settings > Contact Info > Location. Thank you.