If you never displayed your permit then for whatever reason that may be, you would have a valid defence to dispute the charges, were you to do so.
If the fines were paid by the company, then that is effectively accepting the charge. Not receiving the appeals letter would be down to the letters being sent to the registered address of the vehicle which would be the company address.
If the fine has now gone to debt collection, then presumably the debt would be issued against the registered keeper and not you personally as you did not receive the letters. Debt collection also does not necessarily mean court, but if payment is not received then they may issue proceedings to recover the debt at court and if you are not receiving the letters then judgment may be enforced. It is important to know where these letters are going to protect your position.
Lastly, the picture you posted states local authority, and this is very different from a private company issuing a fine. If it is a local authority like a council then it is advisable to pay the fine, as the consequences are more severe, but if it is a private company then as stated, it is just an invoice and should be defended.
It appears all the charges are being dealt with by your company and if this is the case, then you may be bound by the terms of your contract if they are paying these fines on your behalf.