had LR 5,4 standalone upgraded to 5.7 over a year ago, everything worked smoothly. App one week ago, LR couldn't complete catalog back-up anymore and now simply doesn't start up when I double click the icon.
Tell us exactly what happens. Tell us the exact complete unedited word-for-word error message.
problem solved, removed and re-installed LR 5.7.
In hindsight (and with a lot of guessing), something went wrong with the catalogue saving and backing-up, either LR or the Samsung SSD corrupted both versions, hence LR stopped working. Luckily I have off-line backups as well, so all in good order now