Please don't post your serial number online since it is considered personal information.
Unfortunately if you are getting an error like "unable to contact recovery server", then it most likely means Apple has turned off the server providing that particular version of macOS.....we've seen lots of reports like this for the past several months, although i have also seen a few people which seem to be able to reinstall an older OS through recovery mode so it is not completely clear what is going on. If you are receiving some other error, then it may mean you have some other network related issue if you are receiving a negative error code, or maybe the installer certificate has expired (error won't directly mention this though).
Try booting into Internet Recovery Mode using Command + Option + R to see if you can access the later macOS 12.x Monterey online installer. You can install this OS to an external USB3 drive which then will give you access to download & extract the 10.12 installer so you can attempt to make a bootable macOS 10.12 USB installer. However, this functionality of the 10.12 installer has been broken for many years since Apple decided not to fix the installer (Apple hid it for years instead of making one simple character change to the installer). I will have to wait until I'm my other computer to provide a link to the instructions to fix the 10.12 installer. However, if the internal drive is failing, then it may not be possible to install macOS 12.x Monterey since the later macOS installers insist on updating the system firmware using the internal drive....even the macOS 10.13 installer will need to update the system firmware.
The only reliable method of creating a bootable macOS USB installer is by using another compatible Mac using the instructions in this Apple article (macOS 10.12 is broken, so extra instructions are needed):
Create a bootable installer - Apple Support
Here is an article which can help you identify other compatible Macs:
https://eshop.macsales.com/guides/Mac_OS_X_Compatibility
Generally, you need a Mac from 2007 to 2015 to create a bootable macOS 10.11 USB installer. Or a Mac from Late-2009 to mid-2018 to create a bootable macOS 10.13 USB installer.
There really is no reason to restrict yourself to the 10.12 Sierra OS unless you have a third party app that won't run on a later version of macOS. AFAIK, the only apps I've ever seen mentioned were one or two third party audio apps. At the very least most software should be compatible up to at least 10.14 Mojave.
As @Jack-19 mentions, we definitely need more information on the overall problem requiring you to reinstall macOS. Not knowing this had me limit my options to assist you here. You thought you were asking a simple question, but it is actually a lot more complex than you thought which is why people should provide a little more details when asking for assistance.
Edit: I suggest trying to run the Apple Diagnostics to see if any hardware issues are detected. Unfortunately the diagnostics rarely detect issues, but maybe we can get lucky and it will confirm a hardware failure of some sort.....hopefully a drive failure which would be most likely. You can also try booting into Safe Mode to see if that allows you to boot this Mac so you can use DriveDx to check the health of the drive(s) and post the complete text report here using the "Additional Text" icon which looks like a piece of paper.
