.tran (transient analysis) separates a simulation into two parts: first, it solves for the DC solution, and then, based on that DC solution, it starts the time-domain simulation.
The errors you received are all related to being unable to solve the DC solution (refer to this post):
Pseudo transient analysis? - QSPICE - Qorvo Tech Forum
Convergence issues are particularly common when solving the DC solution for switching circuits (as switching circuit is bistable); therefore, you normally need to force initial conditions (i.e., what all currents and voltages should be at t=0s).
There are multiple ways in SPICE to force an initial condition—for example, using UIC in .tran (not recommended, but very commonly used.), adding startup to the DC input (the method you used), or using .ic to force initial conditions.