Help getting started with Roku devices, including setup, connecting your device to your TV, linking a Roku device to your account at my.roku.com/link, adding channels, subscribing to services, and more.
Go to Settings->System->About and it will show whether it's installed. If it shows "not installed", ensure the card it inserted fully. I believe it should be flush with the case when fully inserted. Also, try restarting your Roku 3 from the settings menu or just unplug the power for a few seconds and plug it back in.
Searching this topic, this seems to be a very common problem for Roku 3. Roku should acknowledge the problem and not make us waste so much time.
Well, depending on which model of Roku 3 you have, it's either 5 or 7 years old. It could just be dust in the slot, or yes it could be a hardware problem. But you aren't losing much without having the card installed. It doesn't make the Roku any faster or perform better. It simply expands the storage space for channel installation. Unless you have a lot of different channels that you regularly use constantly, you'll never notice any difference. And if you do have to download the channel again to run after not using it for some time, you're only talking about 10 seconds or so to re-download the code.
Dan Roku Stick (3600), Ultra (4640), Ultra (4670), Ultra (4800), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.
Same for me and my Roku 3. Bought a 4GB card and tried it without luck. Bought the 2GB card directly from Roku and still no luck. It's not dust in the slot because the slot is covered by the HDMI connector. I echo the previous advice - don't bother adding an SD card if you have a Roku 3.