Call 1-888-944-9400 or visit a local store. Request a SIM swap or device diagnostic if you’ve completed all steps above.

Inspect for visible damage, scratches, or corrosion on the gold contacts. Clean the gold contacts gently with a dry, lint-free cloth.

Ensure your S5 is running the latest available firmware, as outdated software can lead to network compatibility errors. Physical Troubleshooting

Here’s a complete explanatory text you can use for troubleshooting or sharing information about the “Invalid SIM Card” error on a US Cellular Samsung Galaxy S5:

The "Invalid SIM" error on a typically stems from a physical connection issue, outdated network settings, or a carrier-specific lock. Because this model is older, hardware wear and tear on the Micro SIM slot is a frequent culprit. Immediate Physical Fixes