How do I connect to the remote site (WR router on static IP sim) from my office (WR router dynamic sim)?

Hi

if you look at the documents section of DIGI website
https://www.digi.com/support/productdetail?pid=5501&type=documentation

There are a number of diffrent ways from VPN using IPsec / OpenVPN or using GRE

this all depends on the type off access and what you are trying to connect to.

as the hq has a dynamic address then HQ would make / initiate the connection.

if the address are public you could use dynamic dns to be able to find the hq ip address from the remote site.

regards

James