Let's do the troubleshooting below, chrystij.

Here’s how:

1. On your keyboard, click on the Start menu and select Settings.
2. Choose Apps, then select Default apps.
3. Next, choose which default you want to set and select Adobe Acrobat Reader.
4. To select a default app by file type, scroll down and select Choose default apps by file type.

To reset the Display PDF In Browser preference, follow these steps:

1. In Reader or Acrobat, right-click the document window, and choose Page Display Preferences.
2. From the list at left, select Internet.
3. Deselect Display PDF in browser, and then click OK.
4. Try to open the PDF again from the website.
5. Re-enable Display PDF in browser to reset functionality, and then click OK.

Let me know if this works for you. You can always leave a reply if you need further assistance.