I have selective as well but I have chosen to ignore it for a while. If I select normal it doesn't save it anyway as if I re open msconfig it reverts back to selective
https/answers.microsoft.com/en-us/windows/forum/all/cant-boot-windows-10-in-normal-startup-use/21954bdc-ae0b-4db5-b9a7-2ed5e4a61e5d
One suggestion I found was try to make the changes to MSCONFIG while in safe mode
go to settings/update & security/recovery
under advanced startup, click restart now button
choose troubleshoot
choose advanced
choose start up options
hit the restart button
choose a safe mode (it doesn't matter which) by using number associated with it.
Pc will restart and load safe mode
Run MSCONFIG and try to select normal startup and apply
reopen it to see if changes accepted. If it does, restart PC as it should be in normal startup
Let me know how you went