Their 'cannot' means: lacks proximate and complete power
Thesis X. These theologians teach that after the fall a person cannot perform even one good work without such efficacious aid from God bending and determining the will toward the good. They mean this of proximate and complete power. All they intend is that, so long as the efficacious grace that a sick and listless will needs for a given good work is missing, a person is not proximately and completely able to do it.
Since this grace, efficacious of itself, grants both the willing and the proximate and fullest ability together, anyone without it lacks the willing and the proximate ability that it supplies.
Latin
X. Porro quod docent illi Theologi ne unum quidem bonum opus ab homine post lapsum posse fieri, absque ejusmodi Dei auxilio efficaci voluntatem ad bonum flectente & determinante, intelligunt de potentia proxima & completa: nec aliud per hoc significatum volunt, quam hominem non esse proxime & complete potentem ad bonum aliquod opus faciendum, quamdiu abest gratia efficax, ad illud propter voluntatis morbum & languorem necessaria. Cum enim gratia haec per se efficax simul det velle & posse proximum & completissimum, quicunque hanc gratiam non habet, is non habet velle & posse proximum quod illa largitur.