Can you repeat the access attempt on the phone and then check the log to check if the connection attempt made it to Jellyfin? Or did the connection attempt fail at Apache? Did your cert recently update?
Jellyfin 10.10.3 (Docker)
Ubuntu 24.04 LTS
Intel i3 12100
Intel Arc A380
OS drive - SK Hynix P41 1TB
Storage
3x WD Red Pro 6TB CMR in RAIDZ1 (JF Library)