Create a new account "new GCkey" > create and submit new EE profile via the new account > link it to your old account
I had the same issue and raised a web form and got the following reply from IRCC
"Thank you for contacting Immigration, Refugees and Citizenship Canada (IRCC).
We verified the information you provided. Since you already have a permanent residence application linked to your online account, the system will not offer the option to start an Express Entry (EE) profile simultaneously in the same account.
If you want to submit an EE profile, you may create a new online account and submit a profile via this new account.
Once the profile has been submitted, you will have the option to link your EE profile to your previous online account if you would like."
Thank you very much. This worked! appreciate the help