Try this solution
Turn on the earbud manually
Note: Always ensure that the earbuds are running the lasted firmware version (V9.0.1). This should ensure that the earbud's performance is not affected by known issues and bugs.
The M1+ earbuds should always power off when placed in the case. But if the correct contact was never made between the pins and earbud then the buds don't register to be in the case and therefore require manual power on, as if they were left out of the case for a few hours.
If it seems like your M1+ earbuds are not powering on out of the case or being found by your mobile device then we would suggest you manually power on the earbuds. To do this please follow the steps below:
1). Take out both the earbuds from the case
2). Please make sure that both M1+ buttons (on Left and Right bud) are pressed and held at the exact same time for 3 seconds and that there is no delay between the button presses, that is, the press should be SYNCED. You will hear a voice prompt for "Power Off" after 3 seconds.
3). Put the earbuds back in the case. They should now show 'breathing' white light while charging.
4). The earbuds are now ready to use. You can take the earbuds out of the case again to pair them to your device.
5). If both earphones’ LEDs are flashing white, then neither of them is waiting to pair. Touch the control surface on ONE earphone, it doesn’t matter which one, for about 3 seconds until the voice prompt says ‘waiting to pair’ and the LED flashes blue and white alternately. One earphone must be waiting to pair.
To check that the earbuds have been placed back in the case correctly again when you have finished using them we recommend that you always check that the LED sequence is showing the breathing white LED pattern on the buds. This means that the earbuds are sitting properly in the case.
When connected to a power source, does the LED lights on the front of your charging case light up?
Try a different charging setup
Try using another power source or another cable to see if the problem persists.
You can also try using the current setup with another device to rule out any fault specific to your charging case.