Sonicwall Global VPN Client can no longer connect to Sonicwall TZ300

penguins_rule used Ask the Experts™
Sonicwall Global Client VPN cannot connect to Sonicwall TZ300.
The VPN which has Spectrum as the ISP cannot connect to the Data Center on port 500 which has Comcast ISP. It attempts to connect. Sonicwall error log has Received packet retransmission. Drop duplicate packet.
It had connected with no problems until yesterday. Other VPNs on different ISP can connect without any problems.
Is there a problem between the two ISP?
There was another person with same problem down the street. Changed her ISP and cable modem and can connect without any problems now.
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Distinguished Expert 2018

Could come down to the modem that you have. Perhaps try replacing it with your own unit, along with router? (Of course I'm assuming that you have ISP-provided equipment now)
Distinguished Expert 2017

check with your ISP to confirm they are not blocking port 500 after you confirm that the LAN IPs you have are not in conflict with the remote IPs.

Try this
Open a command window and run
ping /t
Activate the sonicwall VPN while you have full view of the ping, and see whether during the Bon setup attempt, the ping encounters packet failures.

Change the LAN IPs on your local LAN and see if that fixes the issue.
Received packet retransmission. Drop duplicate packet

I don't think this is an issue of port blocking, the error reported suggests there's something else going on

Have you checked / Verified the client settings?

On the computer where GVC is installed, make sure the NAT Traversal option is disabled under Connection Properties / Peers / Edit / NAT - Traversal.

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Was resolved at one location: Rebooted all modem, computer at Remote site. Moved cables around. For some reason it now works.
The other location changed ISP and modem and it works.

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