thank you Ed,
$ sane-find-scanner I get :
found USB scanner (vendor=0x03f0 [HP], product=0xac11 [
Deskjet 2510 series]) at libusb:003:006
yes, on my computer it is installed hplip - and I also tried to run hp-plugin..
I don't remember if I needed hp-setup for the first installation.
I also tried to reinstall xsane but this wasn't enough (the file of setup remained) .
xsane worked good for much time as till I made samting wrong ... (in the setup panel (?))
I rewrite the content of journalctl...
Aug 25 11:18:04 localhost.pluto xsane[2791]:
scan/sane/http.c 300: unable to open HP-LEDM-SCAN channelAug 25 11:18:04 localhost.pluto xsane[2791]:
scan/sane/bb_ledm.c 531: unable to open http connection hp:/usb/Deskjet_2510_series?serial=CN34B3JGDN05TX