No puedo bloquear celdas en excel

If you want to lock only some cells, the following may help, assuming you want to lock only cells A1 and A2:

1. You select the entire sheet. To do this, select the box that is to the left of column A and above row 1, in the very corner.

2. On the Home tab, in the Alignment group, click the small arrow to open the Format Cells pop-up window.

3. On the Protection tab, uncheck the Blocked box and then click OK to close the pop-up window.

4. Next, you select cells A1 and A2 and do the same procedure, but now you activate the Blocked box

5. Now you go to the Review tab, in the Protect group, click where it says Protect Sheet and accept, if you want, give it a password.

6. Cells A1 and A2 should already be locked; and the rest you can edit whenever you want.

I hope it has helped you, let me know and if it was not like that, please tell me.
Greetings from Peru.