WebSocket connection to 'wss://localhost:7687/' failed: Error in connection establishment: net::ERR_CONNECTION_CLOSED

I make a folder and run npm i neovis.js@alpha, then load this script. I get this error in the browser console:

browser-channel.js:312 
        
       Neo4j driver is configured to use secure WebSocket on a HTTP web page. WebSockets might not work in a mixed content environment. Please consider configuring driver to not use encryption.
(anonymous) @ browser-channel.js:312
(anonymous) @ browser-channel.js:254
t @ browser-channel.js:51
o @ connection-channel.js:93
e.createChannelConnection @ connection-channel.js:95
C._createChannelConnection @ connection-provider-pooled.js:109
e._createConnection @ connection-provider-pooled.js:133
(anonymous) @ pool.js:236
(anonymous) @ pool.js:51
(anonymous) @ pool.js:32
(anonymous) @ pool.js:26
r @ pool.js:22
t._acquire @ pool.js:187
t.acquire @ pool.js:105
e.acquireConnection @ connection-provider-direct.js:102
t.initializeConnection @ connection-holder.js:79
t._run @ session.js:152
t.run @ session.js:131
value @ neovis.ts:369
draw @ test.html:84
onload @ test.html:90
test.html:85 t
browser-channel.js:45 
        
       WebSocket connection to 'wss://localhost:7687/' failed: Error in connection establishment: net::ERR_CONNECTION_CLOSED
n @ browser-channel.js:45
(anonymous) @ browser-channel.js:205
t @ browser-channel.js:56
o @ connection-channel.js:93
e.createChannelConnection @ connection-channel.js:95
C._createChannelConnection @ connection-provider-pooled.js:109
e._createConnection @ connection-provider-pooled.js:133
(anonymous) @ pool.js:236
(anonymous) @ pool.js:51
(anonymous) @ pool.js:32
(anonymous) @ pool.js:26
r @ pool.js:22
t._acquire @ pool.js:187
t.acquire @ pool.js:105
e.acquireConnection @ connection-provider-direct.js:102
t.initializeConnection @ connection-holder.js:79
t._run @ session.js:152
t.run @ session.js:131
value @ neovis.ts:369
draw @ test.html:84
onload @ test.html:90
neovis.ts:99 
        
       Neo4jError: WebSocket connection failure. Due to security constraints in your web browser, the reason for the failure is not available to this Neo4j Driver. Please use your browsers development console to determine the root cause of the failure. Common reasons include the database being unavailable, using the wrong connection URL or temporary network problems. If you have enabled encryption, ensure your browser is configured to trust the certificate Neo4j is configured to use. WebSocket `readyState` is: 3

    at new t (result.js:239)
    at t._run (session.js:165)
    at t.run (session.js:131)
    at t.value (neovis.ts:369)
    at draw (test.html:84)
    at onload (test.html:90)

The library author says that it works on their pc without certificate and on hosted neo4j sandbox, so they can't help me much.

Below is the network tab: