I have tried to get LastPass support to respond to this issue and they continue to defer to the web site providers as the solution. Those companies are NOT going to change their sites to suit a problem endemic to LastPass.
LASTPASS, GET OFF YOUR ASS AND FIX THIS PROBLEM!!!!
Seems to be a Firefox issue - I have 57.0.4 and tried everything suggested previously. Opened up Safari and without changing anything else it worked a charm.
Same finding as ohbejoyful, CapitalOne login sites (various) will not AutoFill when using Firefox (58.0.1), gotta cut & paste ID & Pass. But does great with Safari (iOS 10.13.3, Safari 11.0.3). Same LP, same CapitalOne account, hey Mozilla...