404 error – Wooocommerce + printful, permalinks set

And I forgot, here is the content of Status tab after the above actions:

Connection to Printful API FAIL
Printful API key is set FAIL
WordPress Permalinks OK
WordPress version OK
WooCommerce API enabled OK
WooCommerce Webhooks FAIL
WooCommerce API keys are set OK
WooCommerce authentication URL access OK
WordPress remote requests OK
Recent store sync errors FAIL
Write permissions OK
PHP memory limit OK
PHP script time limit OK

Hey,

Thanks for reaching out to us! After checking your website and your provided details it looks like that there might be some kind of server problems on your side. Could you please try it again?

Thanks for your reply, I tried again just now, but still no luck ?? Do you maybe have any further details for me to investigate the server issues?

Hmm.. I guess you should contact your hosting provider to see if there are any restrictions from their side. What hosting provider do you use?

I use a local hosting provider in Poland called az.pl. However, I am still not sure what to tell them, as I do not have any details of the problem except the 404 error on your website. I am pretty sure that if I contact them and say that I have some issues with WooCommerce and Printful plugin connection with no further details they will redirect me either back to you or WooCommerce support. So, before I contact them, can you please let me know what kind of restrictions do you expect the provider to set in this case?

Just to be sure, here is the screenshot of what I see after the step 5 from WooCommerce intgration instructions:
https://www.dropbox.com/s/y3qs5rdvd3lt050/404.jpg?dl=0

Hey there,

Thank you for the update!
To fix this issue, could you try going to your WordPress Settings > Permalinks > Under “Common Settings” choose any link structure other than “Default.” Confirm by pressing “Save Changes.”
Could you then retry connecting your WooCommerce store?

Let me know how that goes! ??

Thanks for your reply, but like I mentioned in the first post – Permalinks are already set to “post name”. Status tab is all green except those 4 checkpoints:

Connection to Printful API FAIL
Printful API key is set FAIL
WooCommerce Webhooks FAIL
Recent store sync errors FAIL

Hey there,

Sorry for the delay in our response!
We checked on this issue in more detail and it appears that we could not place a test order on your store, which is one of the things that our system checks upon authorization.
It looks like our POST requests are failing, which results in a HTTP 404 error.
Could you reach out to your host and ask them to check why we’re unable to make these requests?

Looking forward to hearing from you! ??