Clear blue digital ovulation test solid smiley but didn’t stay static for 48 hours!

Looking for some assistance please ladies. We have been using the clear blue digital ovulation tests (not the advanced with the flashing smiley). The test says once you get a solid smiley meaning your LH surge is should stay displayed on the screen for 48 hours. I have been testing since day 10 and am currently day 14. I had a circle (negative) yesterday in the am and in the pm. This morning I had a solid smiley (positive) but then looked at the reader a few hours later and it wasn’t still displayed. When I retested in the afternoon it showed a circle (negative).

I’m so confused…. I’ve also used these the last two cycles and both time I had the solid smiley showing static for 48 hours.

Has this happened to anyone? Could the test be faulty or is something wrong…

Any advice would be amazing 🙌🏻🙌🏻