I wanted to share some bits of information that I had to figure out the hard way... the really hard way... with over a month of wasted time.
If you just happen to put everything together right to get the Prestashop Fedex Carrier working with freight, well that is fantastic. But I will tell you, there are a lot of ways to get lost along the way and a lot of things that can go wrong. Plus, very little documentation and absolutely NO help from Prestashop. So here are some important notes to remember.
When you install the Fedex Carrier module by Prestashop, no matter how much you think you need to modify the carriers, do NOT change them! Logic says to modify them, but do not. Yes, the weight ranges are not correct in the carriers that the module adds, but somehow it works anyway. If you make changes to the carriers, there is a high probability that it will break the freight features. I learned the hard way.
Do not disable any of the carriers that are installed with the module. You may have been told by Fedex that your account is all set up for "Fedex Freight", but you might discover the module only works with other freight options. For me, the rates are only pulling for the 1, 2, and 3 day freight and ground settings. I can't explain it and apparently neither can Fedex. If your fedex account is not set up for certain options, then those carriers will not be displayed to the customer. Better to just leave them alone.
You must have an account with Fedex Developer so you can use Fedex Web Services. There are instructions for doing this on the Fedex website and a link to it in the module. Be aware that there are random issues with the Fedex developer website that gives you the necessary credentials. You may get website errors. Just keep trying until you are successful. They send you an email with your production password in it. There seems to be intermittent problems with the e-sign process for their disclosures/agreements. Even though you e-sign, the system sometimes does not recognize it. This happened to me several times. Check the bottom of the email for a paragraph that says your production key is either enabled or not enabled. This is what I kept seeing initially “Your Production Key is not enabled to use FedEx Web Services at this time. You need to initiate this process and then the FedEx customer who owns this application needs to review, sign and send us the FedEx Web Services End User License Agreement.” It took many tries to finally get it to say this “Your Production Key is enabled to access all of the Standard FedEx Web Services for Shipping, automatically.”
Note that each time you go through the Fedex Developer Web Services process to obtain a production key for your account, it changes all of your credentials. You cannot mix credentials from a previous key request.
Your Fedex account must have freight and ground enabled within one account. Some people on the web and even at Fedex will give you false information, trying to tell you that ground and freight must be in separate Fedex accounts. That is old and obsolete information. You want everything in one account. Don't waste your time like I did.
If your module is connected to Fedex ok, it will tell you all is well. However, that does not mean that freight is working. It may or may not be working. Don't use that as an indicator.
All of your products that require shipping must have weights and dimensions.
You will still have a problem with "Free Shipping!" showing up in several places for guests who have no signed into an account and entered a shipping address. This is very misleading and will confuse customers. Assuming you are not intentionally using free shipping for any reason, then I suggest you change your language translations that say "Free Shipping!" to something else. I changed mine to "Address Needed". You will need to change that in the Front Office translations and Module translations. If you are intentionally using free shipping, but still have this showing up when it shouldn't, I am not sure what you will do about that. I do not think Prestashop thought this part out very well.
I hope this helps someone. I know there were a lot of people out there asking for help with the Fedex freight options and no one stepped up. Hopefully this saves someone some stress.