Apparently these things are notorious for not giving proper readings, ie you can be in ketosis but it's not showing up on the strip, etc.
This can be true the longer you're in it. Your body is still throwing ketones but it's also become more adept at handling them so less show up in your urine.
I was strongly advised not to let the strips mess with my head.
And yes, as long as it was showing trace or higher that's what mattered. Just being in it. But again, with the false negatives it's hard to know at all.
We rarely use them now. We do our best to stay OP and let the chips fall where they may.