Consul cluster does not work as expected when one of server is down
Based on my understanding of the topology you have described you essential have:

3 Nodes - 2 Servers and 1 Client

This layout is immediately a problem because the clustering protocol that consul uses relys on being able to easily elect a leader, which requires an odd number of servers.

If you consider the failure scenario of a 2 node consul cluster - as soon as a single node goes down your one remaining node cannot achieve consensus by itself because there's no way to get a majority of the servers voting on something.

In the consul docs the consensus protocol is reasonably well described Consensus docs

They even include a summary table which explicitly states how many server members could be lost for varying cluster sizes.

Following their advice, your 2 server cluster cannot withstand any fault because it would then become impossible to achieve quorum.

Really a minimum number of servers for a functional consul cluster is 3.