Why Choose Keith Thomas
• 20 years of experience as a Senior Apple Support Specialist at Apple Computer UK HQ.
• Former Apple Computer UK Mac Support Specialist and Apple Authorised Service Provider background.
• Established and Independent since 2010 for on‑site Apple Support Service – no call centres, no outsourcing, no hardware repairs. Over 25,000+ Apple problems resolved. Unique on-site Apple Support Service. backed up with Independent Apple Telephone Support Assistance.
• Trusted by home users, small businesses, and professionals across London and the South East UK.• Clear, honest, software‑only support. No Hardware Repairs. Expert Apple Consultancy Service.
On‑site Apple Mac Support in London and the South East UK
What this page covers
This guide explains the real reasons a Mac external display stops working, the steps you can try yourself, and when it’s time to get professional on‑site help. It applies to:
• MacBook Air
• MacBook Pro
• iMac (external second display issues)
• Mac mini
• Mac Studio
If your external monitor shows “No Signal”, flickers, won’t wake, or isn’t detected, this page is for you.
The most common reasons a Mac external display stops working
These are the issues that Keith Thomas identifies most often during on‑site visits:
• Incorrect display settings
• Faulty HDMI, USB‑C or DisplayPort cables
• Damaged or incompatible adapters
• macOS display configuration errors
• macOS update issues
• External monitor firmware problems
• Power delivery issues on USB‑C hubs
Quick checks you can do yourself
These steps solve around 50% of external display issues.
Check 1 – Restart the Mac
A restart resets display detection and clears temporary issues.
Check 2 – Check the cable and adapter
Use a known‑good HDMI, USB‑C or DisplayPort cable. Avoid cheap adapters.
Check 3 – Check display settings
System Settings → Displays → Detect Displays.
Check 4 – Ensure the monitor is on the correct input
Most monitors have multiple HDMI/DP inputs — make sure the right one is selected.
If your Mac doesn’t detect the external display
This usually means:
• Cable or adapter issues
• macOS display configuration errors
• Monitor firmware issues
Try:
• Using a different cable
• Restarting the Mac
• Clicking “Detect Displays”
If your external display flickers or goes black
This usually means:
• Faulty cable or adapter
• Incorrect refresh rate
• Power delivery issues
Try:
• Changing the refresh rate in System Settings → Displays
• Using a direct cable (no hub)
• Restarting the Mac
If your external display shows “No Signal”
This usually means:
• Wrong input selected
• Cable or adapter failure
• macOS display configuration issues
Try:
• Switching the monitor input
• Trying a different cable
• Restarting the Mac
When DIY stops working
You should get on‑site help if:
• The external display is never detected
• The display flickers constantly
• The Mac shows display errors after updates
• macOS reinstall does not fix the issue
• You need your data preserved
These issues usually require:
• Display configuration repair
• macOS recovery
• Data‑safe macOS reinstall
• Hardware and cable diagnostics
On‑Site Apple Mac Support – London & South East UK
If your Mac external display is not working, Keith Thomas provides an often same‑day on‑site support service across:
• Central London
• West, North, South and East London
• Surrey
• Berkshire
• Hampshire
• Wiltshire
Keith Thomas is a Mac Support Specialist in:
• External display and monitor issues
• macOS display configuration repair
• Data‑safe macOS recovery
• macOS reinstall and repair
• iCloud and Apple Account issues
• New Mac setup and migration
• Hardware and cable diagnostics
Book on‑site help in London and the South East UK
If your Mac external display is not working, Keith Thomas can visit your home or office and get you working again.
Keith Thomas – Apple Mac Support Specialist
Established 2010 – Open 09:30–20:30, 7 Days
Contact Keith Thomas by Telephone: 07800 940756 or by Text to: 07800 940756, or simply complete an online website contact form 24/7