Is money earned from receiving a salary, despite the cessation of work duties and absence from work due to a holiday, with the manager's knowledge, considered unlawful money (haram)? And what should be done with this money if it is unlawful? And does that affect the acceptance of prayers?

An employee must be present at the workplace for the entire duration of working hours, and absence is not permitted except as allowed by the employer's regulations. You are not entitled to a salary for days of absence without official permission, even if the manager was aware of it and did not communicate. You must repent to Allah by returning the salaries corresponding to the days of absence to the employer. If returning it is not possible, then donate it to the poor or for the benefit of Muslims. If you were present, you are entitled to the salary even if you were not assigned any work. Consuming unlawful earnings (haram (definition)) is among the impediments to the acceptance of supplications. It is not a necessity that every supplication made by someone who consumes haram is rejected, as there might be factors that override this impediment, and performing acts of obedience necessitates the acceptance of supplications.