Sorry for the delay in response to your query. As per the description above, you are not able to convert any PDF, as it's directing you to the Pricing page, Is that correct?
As per the records, you don't have any active subscription on your Adobe Id which you used to login on Adobe Forums, so if you are using this Adobe Id, you will get the message to purchase the service/subscription while converting any PDF file.
If you are using the free Adobe Reader DC, it does not provide the option to convert any PDF file.
You have to log in with the Adobe id on which you have the active license/subscription in order to edit any PDF or use the service.
More information about Convert into PDF: PDF creator, create PDF files | Adobe Acrobat DC
Feel free to update this discussion in case you need further assistance.