Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance
Environment - Non Weather Related; Human Factors
During the crew brief we discussed the departure procedure and I selected LNAV on and confirmed it was armed via the PFD. After a maintenance issue at the gate and a rushed before takeoff checklist during a short taxi we took off. Shortly after takeoff; ZZZ tower asked why we didn't turn. Confused I looked at the PFD and LNAV was not operating. I told the Captain to turn in the correct direction and moved the heading bug to the correct heading. We don't know how or why LNAV disengaged after we both confirmed it was armed in the brief.Rushing the before takeoff checklist caused us not to verify everything in the MCP/ND check so we don't know if LNAV was still armed at takeoff. Other than training in the aircraft type simulator; I have not flown since early November. The Captain only has X00 hours in the aircraft.Suggestion - Don't rush the before takeoff checklist.
First Officer reported LNAV was not engaged during departure resulting in a track heading deviation.