[FIX] Telemetry service was not running. Some achievements popped after completing a race. The rest popped when launching another game which turns out also had some unpopped achievements. Hope this helps someone else if they come across this issue 
Seen a few people having problems with some achievements unlocking in-game at various stages through progression, but since I started playing the game for the first time on Tuesday, nothing has popped at all.
Checked Teredo settings (which were blocked at first) but now all sorted, rebooted PC, completed a couple of races (9 complete in total at the moment), purchased some cars (117 in garage at the moment), mods etc and still nothing.
Played a couple of other games on my PC which popped achievements after all the setting changes and reboots above, so can only see this being a Forza problem as it stands.
Only thing I haven’t done is reinstall (as it took an absolute age to download everything the first time round), but if needs be I can try again.
Stats seem to be coming through to Forza Hub (albeit a day or so behind) and credits are coming in from Forza Hub to the game.
I haven’t tried installing on my Xbox One as it’s currently out of action and don’t have enough room on it anyway to install as it’s an old 500GB hard drive variant that’s maxed out as it is.
Any ideas anyone?!
This is the Forza 7 Ultimate Edition if that makes any difference.
Gamer Tag: Pearce1991
Section of DxDiag Output Below (just in case, can post whole thing if needed):
System Information
Time of this report: 2/15/2019, 11:09:19
Machine name: DESKTOP-PVCICBT
Machine Id: {DE3A9396-C58E-4237-B2F2-DBBA4663B838}
Operating System: Windows 10 Pro 64-bit (10.0, Build 17134) (17134.rs4_release.180410-1804)
Language: English (Regional Setting: English)
System Manufacturer: Gigabyte Technology Co., Ltd.
System Model: Z87-HD3
BIOS: F6 (type: UEFI)
Processor: Intel(R) Core™ i7-4770K CPU @ 3.50GHz (8 CPUs), ~3.5GHz
Memory: 16384MB RAM
Available OS Memory: 16272MB RAM
Page File: 14778MB used, 3924MB available
Windows Dir: C:\Windows
DirectX Version: DirectX 12
DX Setup Parameters: Not found
User DPI Setting: 96 DPI (100 percent)
System DPI Setting: 144 DPI (150 percent)
DWM DPI Scaling: UnKnown
Miracast: Available, no HDCP
Microsoft Graphics Hybrid: Not Supported
DxDiag Version: 10.00.17134.0001 64bit Unicode
DxDiag Notes
Display Tab 1: No problems found.
Display Tab 2: No problems found.
Sound Tab 1: No problems found.
Sound Tab 2: No problems found.
Sound Tab 3: No problems found.
Sound Tab 4: No problems found.
Sound Tab 5: The file L6UX264.sys is not digitally signed, which means that it has not been tested by Microsoft’s Windows Hardware Quality Labs (WHQL). You may be able to get a WHQL logo’d driver from the hardware manufacturer.
Input Tab: No problems found.
DirectX Debug Levels
Direct3D: 0/4 (retail)
DirectDraw: 0/4 (retail)
DirectInput: 0/5 (retail)
DirectMusic: 0/5 (retail)
DirectPlay: 0/9 (retail)
DirectSound: 0/5 (retail)
DirectShow: 0/6 (retail)
Display Devices
Card name: NVIDIA GeForce GTX 770
Manufacturer: NVIDIA
Chip type: GeForce GTX 770
DAC type: Integrated RAMDAC
Device Type: Full Device (POST)
Device Key: Enum\PCI\VEN_10DE&DEV_1184&SUBSYS_11841569&REV_A1
Device Status: 0180200A [DN_DRIVER_LOADED|DN_STARTED|DN_DISABLEABLE|DN_NT_ENUMERATOR|DN_NT_DRIVER]
Device Problem Code: No Problem
Driver Problem Code: Unknown
Display Memory: 10153 MB
Dedicated Memory: 2017 MB
Shared Memory: 8135 MB
Current Mode: 1920 x 1080 (32 bit) (60Hz)
HDR Support: Not Supported
Display Topology: Internal
Display Color Space: DXGI_COLOR_SPACE_RGB_FULL_G22_NONE_P709
Color Primaries: Red(0.625500,0.340344), Green(0.280773,0.595227), Blue(0.155773,0.070813), White Point(0.283703,0.298352)
Display Luminance: Min Luminance = 0.500000, Max Luminance = 270.000000, MaxFullFrameLuminance = 270.000000
Monitor Name: Generic PnP Monitor
Monitor Model: AVT GL310
Monitor Id: AVX0003
Native Mode: 1920 x 1080(p) (60.000Hz)
Output Type: HDMI