TPM Attestation "not ready"

Hello,

Tried to encrypt drives with Bitlocker on OptiPlex3050, but it didn't start. While looking for issues, i found that TPM attestation is not ready and probably it's the reason behind this BitLocker behaviour. I tried updatin BIOS, TPM firmware, clearing TPM but nothing helped. Any ideas, what can be done, to make attestation "ready"?