Hello I need to stop the messages that shows new version of abantecart  is available. How can I do that ? Just want to remove that message all others are fine.

Hello.
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You were right. Probably. I tried saving again this morning and it worked first time. And now I've been able to add all the locations back in, and save the shipping costs, and it's all still working.  So it probably was some kind of server security issue and nothing to do with AbanteCart itself.

Thanks for all your help, Basara! 

I spoke too soon. 

Everything appeared to be working. I decided to use the Weight Based Shipping, and it was behaving as I expected with the two predefined locations (USA and Canada) plus another one I added for testing. So I added 6 more locations - one for each of the zones I needed, and added a bunch of countries to each. The locations show up in the "Additional Settings" section of the Weight Based Shipping plugin, and I can add the shipping weights and prices there. All good so far.

But now when I add some weight/price text in Weight Based Shipping, and click "Save", I get a 403 Forbidden error. The message says it's accessing this:

/index.php?rt=extension/default_weight&s=admin123&token=egotT9qRoiWKpXZMXnW0bp1k9sv2XXhV (port 443)

I've checked the permissions on that file - it's 644, which I believe is correct because all other files have the same permissions. In any case I certainly didn't edit any files or permissions or anything - I was using the admin web interface to add locations and shipping weights. It seems it randomly stopped working.

Some things do still work - like any time there's a little tick box to save individual changes - that seems to work still. But the weight/price text boxes don't have that tickbox. I have to click on the "Save" button at the bottom, and that's when it shows the error.

I tried deleting all the extra locations that I added, leaving just USA defined. So I only see the USA region on the Weight Based Shipping page now, but the 403 error still occurs.

Most of the admin website still works. I can save changes on the Fast Checkout extension page. The only thing I've found that doesn't work is the Royal Mail shipping extension, which now has the same problem. Individual save tickboxes work, but the "Save" button shows that error.  I'm positive I was never seeing any 403 errors before I added more locations.

I've looked in System -> Logs -> Error Logs, but there is nothing in there.

Any ideas?

Wow, thanks. You were absolutely correct, the problem was in the Fast Checkout extension - I didn't even know that was a thing, but I tried disabling it, and the regular checkout process worked more sensibly.

Then I tried your fix, and Fast Checkout is now behaving sensibly too - payment options are not shown at all if shipping cannot be calculated.

I believe I still have an issue with the country lists though. On either the Royal Mail extension, or the Weight Based Shipping extension, is there any way to do the equivalent of "all other countries" as a category?  I see that the Weight Based Shipping uses "locations" as specified in the System -> Localization -> Locations menu, so at least I can create as many international zones as I want. And presumably I can edit the Countries list to disable any countries that I don't want to appear in the selection dropdown that the customer sees. So I guess I could work around the absence of any kind of "all countries not specified so far" type of option in the shipping calculation, but it would be more convenient if there was one.

Also, just in case you're not aware, the regular checkout process seems to have some bad CSS formatting - see screenshot attached. I checked with Edge and Firefox and it looks the same on both. I guess this isn't a big issue if everyone uses Fast Checkout instead, but on the other hand if there's a bug in Fast Checkout then I'm not sure how anyone is using AbanteCart to do shipping?

Apart from these issues, I'm actually pretty happy with AbanteCart though. As I said before, it's better than the others that I tried