Greenwood met with United manager Ole Gunnar Solskjaer on Sunday for an hour after a week which saw him twice make public apologies for off the field indescretions.
Solskjaer plans further talks with his young forward when he gets his full squad back together at Carrington on Monday.
United were not planning to discipline him over what happened in Reykjavik – despite the club's disappointment in him, reports The Sun.
But Solskjaer must now decide how to handle the latest incident – being pictued taking laughing gas - which is believed to have taken place around three weeks ago.
The Norwegian would ideally want Greenwood in his plans – particularly with the move for Jadon Sancho still in limbo.