UEFI Boot into OpenSuSE not possible

I have the problem I cannot boot into TumbleWeed any more. On my Acer Laptop I get the error message “Security boot fail”. After pressing “Enter” a few times the system boots into Windows.
It used to work before an update of Windows 10.
I tried to reinstall the “MBR” using grub2-install and Yast2, but that did not help. So far, I can only boot into TumbleWeed using a bootable USB-Stick containing a TumbleWeed ISO.
I have found this page: https://en.opensuse.org/openSUSE:UEFI, but there is no help repairing the Boot-Loader.
So how can I fix my problem?
Thanks in advance

Since you are able to boot via the install media, I suggest using Yast Bootloader

When at the bootloader screen, change something – I usually change the timeout by 1 second. This should cause the UEFI bootloader to be reinstalled.

If you are trying to do it all at the command line, then you need “shim-install” rather than “grub2-install” (because of secure-boot requirements).