This is happening to me too. Since Friday night MusicBee seems to randomly 'lose' connection with Last.fm. I log back again, the cached songs scrobble as usual, but it soon disconnects again. It doesn't seem to be a problem with Last.fm itself this time around.
My log seems to be slightly different from yours though, here's an example:
17/02/2019 15:30:50 - FAIL: A solicitação foi anulada: O tempo limite da operação foi atingido. - deferred:
Devendra Banhart - Für Hildegard von Bingen