Can't debug using a Huawei P20 Pro phone

I have 2 Huawei P20 Pro phones (wife's and mine).  Neither can debug using the latest RAD studio.  The phone is seen, the programme is copied to the phone, and runs.  But breakpoints are ignored (and starting a progremme with <F8> is just the same as starting with <F9>).  I have done the complete reset of the phone at Huawei's suggestion (and foiund that their cute backup tool does not backup everything, unfortunately for me!), and this made no difference.

I have tried a large number of combinations of options in the "Developer Options" stuff - to no avail.

If I plug the old Samsung S5 in instead of the Huaweis, it works perfectly.

Any ideas please?