I've been using the same ones for years and was able to connect to my fitbit but not my new Garmin Lily.
Is there a way around this so my weight updates automatically?
I do not know what Fitdays is, but the link on the MyFitnesPal website that I posted, claims that you can connect a Fitbit scale to MFP. I do not own any such scale, so cannot confirm it, but should you experience any problems connecting it, reach out to the support of MFP - they are usually rather responsive.
Now the connection between fitdays and fitbit is gone and cant reconnect.
Well, I am afraid that the Garmin user forum is not the best place for giving you tips how to solve problems between Fitdays and Fitbit. You may want to try their own support or community platforms.