I followed your video for setting up a Wordpress sight on my Synology DS-223 and it works perfect. Nice, really nice, video! Once up and running I installed WooCommerce to handle my on-line shop. No problems. Up and running.
Then I started seeing problems. Site health took a hit.
Critical issue: REST API Response: (http_request_failed) cURL error 28: Connection timed out after 10001 milliseconds
Site Security: * Error Your installation of WordPress prompts for FTP credentials to perform updates. (Your site is performing updates over FTP due to file ownership. Talk to your hosting company.)
Loopback test failed: The loopback request to your site failed, this means features relying on them are not currently working as expected.
Error: cURL error 28: Connection timed out after 10001 milliseconds (http_request_failed)
Same cURL error as before. Several other errors also show up, all pointing to cURL.
Did some research and honestly, could not understand any of it. I’m lost. The cURL module in my php setup is checked but what is causing the errors, I have no idea.
Now, I have another script for handling digital downloads, from Vibralogix. I’ve used it on my computer for years. Installed it on my NAS and setup access, no problem. But when I try and upload a file I get a cURL error. Contacted Vibralogix and was told that error is occurring because cURL is not being allowed to call back to itself on my server ( Is that the loopback issue? )
Anyway. If you have a solution to WP cURL issues on the Synology NAS, I’d really like a video on that! Thank you.
Of course, if anyone else reading this has a solution, I’m all ears! 
Okay, not quite there yet but I’m getting close.
Apparently the problem is with cURL trying to do call backs to the same server the script is on and somewhere in the process it’s getting lost.
So after a lot of research and talking to an actual php programmer, we’ve identified the issue. We think.
What needs to happen is I need to map my IP address to the website. Sound easy? It’s not!
The Synology NAS runs on Linux. There is a ‘hosts’ file at /etc that is used specifically to map IP’s and websites. All I have to do is edit the file and add the information to match my IP to my domain name. Sound easy? It’s not!
After more research I found that the only way to access that file is to use a terminal program. Which I’ve never done before. PUTTY was suggested and the first time I tried it would not accept my username and password. Apparently my security was setup to block IP after 3 bad attempts. Yep. Locked myself out of my own NAS. So I went in thru Synology’s Quick Connect and was able to not only unblock my IP but I took the extra 5 seconds and added it to the Whitelist! Back to the terminal. Ditched PUTTY and found what was called a ‘more current’ utility called KITTY. That did it! First try, and I’m in.
Then more research on how to navigate and make changes to a Linux file.
Bottom line, I can edit the file using VIM, which is part of the Linux installation. Made the changes I needed to make, and … couldn’t save the file because it is ‘read only’. More research and I learned how to change file permissions in Linux. Yep. My eyes glazed over just about then!
Entered the data, and … it won’t let me change the permissions!
I have full admin access with read/write permission to everything I can find a setting for, yet, using the terminal program it will not let me change the permissions of that particular file. Or delete it, or overwrite it.
So, can anyone clue me in on ‘how’ to change the file permissions on that file so that I can edit and save it? I am just not up on Linux operations and this is above my skill level apparently. Help!
Problem solved!
The film clouding my vision is fading!
Wordpress now runs flawless! No more cURL issues. No timeouts. No error 28. Perfect!
Following what I did above, once I logged into my NAS I could not modify the hosts file because I did not have write permission even though I had logged in as an administrator.
Turns out, on Linux, you have to be a ‘super admin’. How does that happen? Simple!
Once you log into the NAS as admin, type this sudo -i and press enter.
Re-enter the same admin password you originally logged in with.
You will now be a ‘root’ superuser!
So, I used vim to edit the hosts file, mapping my ip to my website domain. Saved the file ( which now works! ) and exited the terminal program.
Before I did this, when I checked the Wordpress admin panel I was getting several errors on the ‘Health’ of the site. It failed a loopback test and also displayed the cURL error 28.
After editing the hosts file on my NAS, perfect. No errors!
Closing this topic. Thanks for letting me vent here! Hope this information can help someone else.