Hello,
Could you try uninstalling the LastPass app, restarting your device, then reinstalling and making sure LastPass Autofill is enabled in your device's Accessibility settings to see if that resolves the issue?
Thanks for giving that a try. If you're still experiencing this issue after an uninstall and reinstall, so that our team can gather more details and hopefully resolve this issue, could you submit a bug report following the steps outlined here? https://support.logmeininc.com/lastpass/help/how-do-i-report-a-bug-to-lastpass