Dan-cer If using a fork of telegram, sms verification won't work. If using the official telegram app, it might be it is dependant on google play services for this function to work. Also make sure u have all necessary permissions allowed for this function to work.
I amusing a fork of telegram (forkgram) for some niche usecases, mostly as an alternative for ntfy for things happening on my homeserver i want to be notified about, or when my tar1090 instance spots a military plane in a radius of 30km of my house, just out of interest and its fun.
I don't really remember how i have set it up but i don't have play services enabled. It could be i created another profile specific for this usecase with google play services and then 'migrated' to forkgram, but unsure what the process was.