Connection suddenly fails to Synology NAS

[TomBombadil]

Synology NAS connection no longer works.
I noticed today that the connection to my Synology NAS via OpenVPN no longer works. Nothing has been changed in the device configuration. Access can no longer be established via two different clients.

Pls find the following log with error messages:

Thu Dec 7 14:46:17 2023 WARNING: Compression for receiving enabled. Compression has been used in the past to break encryption. Sent packets are not compressed unless "allow-compression yes" is also set.
Thu Dec 7 14:46:17 2023 DEPRECATED OPTION: --cipher set to 'AES-256-CBC' but missing in --data-ciphers (AES-256-GCM:AES-128-GCM:CHACHA20-POLY1305). OpenVPN ignores --cipher for cipher negotiations.
Thu Dec 7 14:46:17 2023 OpenVPN 2.6.6 [git:v2.6.6/c9540130121bfc21] Windows-MSVC [SSL (OpenSSL)] [LZO] [LZ4] [PKCS11] [AEAD] [DCO] built on Aug 15 2023
Thu Dec 7 14:46:17 2023 Windows version 10.0 (Windows 10 or greater), amd64 executable
Thu Dec 7 14:46:17 2023 library versions: OpenSSL 3.1.2 1 Aug 2023, LZO 2.10
Thu Dec 7 14:46:17 2023 DCO version: v0
Thu Dec 7 14:46:18 2023 WARNING: No server certificate verification method has been enabled. See http://openvpn.net/howto.html#mitm for more info.
Thu Dec 7 14:46:18 2023 TCP/UDP: Preserving recently used remote address: [AF_INET]80.254.188.156:1194
Thu Dec 7 14:46:18 2023 UDPv4 link local: (not bound)
Thu Dec 7 14:46:18 2023 UDPv4 link remote: [AF_INET]80.254.188.156:1194

What is the cause? In this respect, it is a mystery that no modifications have been made to the system.
Many thanks for your much appreciated help!