Berechnung Summe ist immer "Null" Excel on Mac

Panonra7660 

Perhaps Excel sees the values as text even though the cells are formatted as numbers.

Things to try:

• Select a column with such values. On the Data tab of the ribbon, click Text to Columns, then click Finish.
• Alternatively, select an empty cell and copy it. Then select a range with values that won't sum. Click the lower half of the Paste button and select Paste Special...
  Select Add, then click OK.