BG77+PSM+LTEM not enter PSM

Hello, I am working with the BG77 module and facing an issue with entering Power Saving Mode (PSM). As you can see below, I received the URC [+QPSMTIMER: 3600,0], but my device cannot enter PSM. The proof is that I don’t receive the PSM POWER DOWN indication. Hope your help.

hello? Can you help me solve this problem?