Faced an incomprehensible problem.
When trying to open a workbook, an exception is thrown:
ArgumentOutOfRangeException: Index and count must refer to a location within the string. (Parameter 'count')
At the same time, everything works fine on the working computer during development, there is no exception.
The problem pops up when placing a project on a hosting.
The library from Syncfusion in a similar environment opens the file normally on the hosting.
Library version 2020.3.1019
.net5 Server-side project