This error usually indicates that, whilst the user has been allowed (or chosen) as the designated approver for this transaction type. They currently do not have the correct security permissions to access the Purchase Requests approval module.
You will need to know and have access to your CLOUD\DMnnnnHosting.Admin account in order to follow the steps below:
In a Web Browser, browse to the FinOps Remote App Gateway and log in with your Hosting.Admin account
Launch FinOps Administrator and connect to the correct Database
Click System Control, Security Profiles.
Select the required profile, click Edit
On the Security tab, on the left hand pane, select the folder Authorisation
On the right hand pane, check Purchase Requests has a green tick.
If it doesn't, double-click to enable it.
Click OK to save the changes
Now the user may need to log out and back in for these changes to take affect. The user should now have access to the Purchase Requests approval module.