Allow siri when locked is disabled and cannot turn on,

Hello KTorosyan,

It sounds as though the option for Allow Siri When Locked may be grayed out, preventing you from enabling that feature. If so, there's a possibility this may be due to having Content & Privacy Restrictions enabled. To check this setting and disable it, you'll want to follow the steps listed below. You can also find more information about this setting in the article below.

1. "Go to Settings and tap Screen Time.
2. Tap Turn on Screen Time, then tap it again. Choose "This is My [Device]" or "This is My Child's [Device]."

• If you're the parent or guardian of your device and want to prevent another family member from changing your settings, tap Use Screen Time Passcode to create a passcode, then re-enter the passcode to confirm. After you confirm your passcode you'll be asked to enter your Apple ID and password. This can be used to reset your Screen Time passcode if you forget it. 
• If you're setting up Screen Time on your child's device, follow the prompts until you get to Screen Time Passcode and enter a passcode. Re-enter the passcode to confirm. After you confirm your passcode you'll be asked to enter your Apple ID and password. This can be used to reset your Screen Time passcode if you forget it. 

3.Tap Content & Privacy Restrictions. If asked, enter your passcode, then turn on Content & Privacy Restrictions."

Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support

Let us know how that goes!

In addition to Community Specialist Todd0213’s excellent advice, if you have a business or school email account on your iPhone the organization’s IT management can control many privacy functions of your phone.