"It is connected" vs "It connected"

"It is connected..." means that it is currently possesses the 'connected' attribute. "Is" is present tense as opposed to the past tense of your other line. 'Connected' acts not as a verb, but an adjective. See https://www.grammarly.com/blog/adjective-and-verb-placement/

"It connected..." means that it made a connection in the past. Connected is a verb in the past tense. It could still be connected, but it might not be. At some point in the past, it was.