Does your manager have a manager who you can contact? Or is there another higher up?
Unless your employer literally is a small handful of people you shouldn't be in the position where you have no-one you can contact more or less straight away with a problem, certainly with an acknowledgement with a plan of action the same day, from a person, not an automated email. What if you had an urgent work issue, eg an unsatisfied customer?
On Tuesday you need to push for an explanation and preferably a same day transfer of your salary.
And it really could be an error, these things happen at all stages through the payroll process. I work for a large employer that makes endless mistakes, or they've happened in the banking system.
Salaries paid to the wrong people, meaning the director's salary has been paid to someone in a junior role, people not being paid at all, overtime or shift allowances not being paid, mistakes with deductions for tax free childcare, meaning money for childcare has been deducted from salary but not appeared in the childcare account, you name it, it's happened, multiple times.
But there's always been a route to get things sorted, as should be the case for you, unless there's something you're not mentioning. If there was a formal dispute between you and your employer, it would be very unwise and unusual of them to deliberately not pay you, without any explanation.