As I understand it, when you wrote this, you were using Juggluco for four days and didn’t have connection problems on day three and four, but earlier you experienced long periods without receiving glucose values via Bluetooth. Thus in principle it is working.
A screenshot of the sensor screen (the screen where you also found “forget” and “reenable”) during such a long period of connection problems would be useful to see where the problem is located.
If Juggluco doesn’t manage to receive glucose values from the sensor, it is generally useful to force close the app that previously had a Bluetooth connection with the sensor (in your case the Canadian Libre 2 app).
Turning Bluetooth off and on can help.
Also scanning the sensor a few times with a few minutes between is sometimes necessary.
It can happen that a sensor has long periods of unsolvable connection problems. Also some smartphones or smartwatches seems to have less connection problems than others. (Naturally you also have to stay near your smartphone.)
My current smartphone has very few connection problems (receiving 97% of the glucose values), but I have also experienced sometimes hours of connection problems for no apparent reason.