Accounting reports have a significant amount of data. A year-to-date report for the end of the year can take in excess of fifteen minutes, depending on the size of the practice. If you are using a slow computer or have a slow internet connection, it can take even longer.
You can break the report up into date ranges of smaller increments, try a different computer, or run the report at a time of the day when other computers in the office are not being used.