Can I manually reattempt restoring SMS messages from backup? I have a Nexus 5X updated to the latest Android version. I did a factory reset and chose to restore everything from backup. But my SMS messages are gone. I'm pretty sure the SMS backup was activated in the settings - after all, everything else got backed up and restored just fine. Has anyone else had this problem? Is there some manual way for me to reattempt the restore from backup?
I'll skip the basic parts where you know that a factory reset wipes the phone and address to what I believe to be the core of the question - 


  Is there some manual way for me to reattempt the restore from backup?


I'm not totally sure if you ended up with an upgraded version of Android (from what version to what) or if you 'chose to restore everything from backup'.
Depending on the details here you could face the issue where you, even if you have a backup of the SMS database it may not be directly usable by a different Android version.

The SMSes are stored in a sqlite database, typically a file called 
mmssms.db. On my phone it is located at the following location (a typical one) - shown for me by this command on my Android;

find / -iname '*sms*.db' 2&amp;&gt;/dev/null
/data/data/com.google.android.gms/databases/icing_mmssms.db
/data/data/com.google.android.gms/databases/ipa_mmssms.db
/data/user/11/com.google.android.gms/databases/icing_mmssms.db
/data/user/11/com.google.android.gms/databases/ipa_mmssms.db
/data/user_de/0/com.android.providers.telephony/databases/mmssms.db
/data/user_de/11/com.android.providers.telephony/databases/mmssms.db
1|herolte:/data #


The key file here is

/data/user_de/0/com.android.providers.telephony/databases/mmssms.db


Even if you may not be able to use this db on your (possibly newer/different) Android, you can always see/extract the messages inside using a tool on a PC for instance. Search for 'sqlite browser'.
You will have to decide if you need assistance with handling the SQL tables/format, but it should be easy enough to browse read-only.
(And, of course, always back up stuff before trying out changes.) That you do have a backup is very positive.

You could also (less manually) search for tools/apps that possibly not only backs up the SMS'es, but perhaps are able to restore from your backup. Also in this case case may the key file in question be the file mentioned above.