Error after compiling WebGL

After compiling the project under WebGL, I open the project in the browser. After loading the project in the window, everything that is displayed is a black screen. Then, after a while, a window with the error text is displayed:

 An error occurred running the Unity content on this page. See your browser JavaScript console for more info. The error was:
 uncaught exception: abort(84) at jsStackTrace (BuildOne.asm.framework.unityweb:1154:12)
 stackTrace (BuildOne.asm.framework.unityweb:1168:11)
 abort (BuildOne.asm.framework.unityweb:19737:43)
 nullFunc_iii (BuildOne.asm.framework.unityweb:15419:2)
 b84 (BuildOne.asm.code.unityweb:1947847:1)
 _MySqlConnectionStringBuilder_AddKeywordFromProperty_m2956903219 (BuildOne.asm.code.unityweb:722938:1)
 _MySqlConnectionStringBuilder_Initialize_m2269781082 (BuildOne.asm.code.unityweb:1238663:1)
 _MySqlConnectionStringBuilder__cctor_m3340290325 (BuildOne.asm.code.unityweb:1519450:1)
 __Z31RuntimeInvoker_Void_t1185182177PFvvEPK10MethodInfoPvPS4_ (BuildOne.asm.code.unityweb:1886979:1)
 dynCall_iiiii (BuildOne.asm.code.unityweb:1888511:1)
 invoke_iiiii (BuildOne.asm.framework.unityweb:15981:10)
 __ZN6il2cpp2vm7Runtime6InvokeEPK10MethodInfoPvPS5_PP15Il2CppException (BuildOne.asm.code.unityweb:1600647:1)
 __ZN6il2cpp2vm7Runtime9ClassInitEP11Il2CppClass (BuildOne.asm.code.unityweb:924707:1)
 __ZN6il2cpp2vm6Object16NewAllocSpecificEP11Il2CppClass (BuildOne.asm.code.unityweb:1524584:1)
 __ZN6il2cpp2vm6Object3NewEP11Il2CppClass (BuildOne.asm.code.unityweb:1917052:1)
 _MySqlConnection__ctor_m3540817235 (BuildOne.asm.code.unityweb:1638499:1)
 _MySqlConnection__ctor_m3723565411 (BuildOne.asm.code.unityweb:1843884:1)
 _BuildMine_ConnectForBase_m977522447 (BuildOne.asm.code.unityweb:1166948:1)
 _BuildMine_CalculationForModels_m3790094255 (BuildOne.asm.code.unityweb:87401:1)
 _BuildMine_Start_m3620171236 (BuildOne.asm.code.unityweb:1920984:1)
 __Z31RuntimeInvoker_Void_t1185182177PFvvEPK10MethodInfoPvPS4_ (BuildOne.asm.code.unityweb:1886979:1)
 dynCall_iiiii (BuildOne.asm.code.unityweb:1888511:1)
 invoke_iiiii (BuildOne.asm.framework.unityweb:15981:10)
 __ZN6il2cpp2vm7Runtime6InvokeEPK10MethodInfoPvPS5_PP15Il2CppException (BuildOne.asm.code.unityweb:1600647:1)
 _il2cpp_runtime_invoke (BuildOne.asm.code.unityweb:1816608:1)
 __Z23scripting_method_invoke18ScriptingMethodPtr18ScriptingObjectPtrR18ScriptingArgumentsP21ScriptingExceptionPtrb (BuildOne.asm.code.unityweb:1694437:1)
 __ZN19ScriptingInvocation6InvokeEP21ScriptingExceptionPtrb (BuildOne.asm.code.unityweb:1242209:1)
 __ZN13MonoBehaviour30InvokeMethodOrCoroutineCheckedE18ScriptingMethodPtr18ScriptingObjectPtrP21ScriptingExceptionPtr (BuildOne.asm.code.unityweb:412903:1)
 __ZN13MonoBehaviour30InvokeMethodOrCoroutineCheckedE18ScriptingMethodPtr18ScriptingObjectPtr (BuildOne.asm.code.unityweb:1214796:1)
 __ZN13MonoBehaviour16DelayedStartCallEP6ObjectPv (BuildOne.asm.code.unityweb:1473372:1)
 __ZN18DelayedCallManager6UpdateEi (BuildOne.asm.code.unityweb:684056:1)
 __ZZ23InitPlayerLoopCallbacksvEN50EarlyUpdateScriptRunDelayedStartupFrameRegistrator7ForwardEv (BuildOne.asm.code.unityweb:1748364:1)
 __Z10PlayerLoopv (BuildOne.asm.code.unityweb:550238:1)
 __ZL8MainLoopv (BuildOne.asm.code.unityweb:1304636:1)
 dynCall_v (BuildOne.asm.code.unityweb:1949421:1)
 browserIterationFunc (BuildOne.asm.framework.unityweb:9294:4)
 runIter (BuildOne.asm.framework.unityweb:8694:5)
 Browser_mainLoop_runner (BuildOne.asm.framework.unityweb:9332:3)

The application uses a connection to the database, I assume that it is because of this that there are errors. I do the connection to the database in the following way:

 string serverName = "192.168.1.3";
         string userName = "name";
         string dbName = "BaseData";
         string port = "3306";
         string password = "password";
         string connStr = "server=" + serverName +
             ";user=" + userName +
             ";database=" + dbName +
             ";port=" + port +
             ";password=" + password + ";";
         MySqlConnection conn = new MySqlConnection(connStr);
         conn.Open();                                           
         string sql = "SELECT e.id id, c1.x x1, c1.y y1, c1.z z1, c2.x x2, c2.y y2, c2.z z2, p.title " +
             "FROM edge e JOIN place p ON e.place_id = p.id JOIN conjunction c1 ON e.conjunction_start_id = " +
             "c1.id JOIN conjunction c2 ON e.conjunction_end_id = c2.id WHERE `e`.`id` < 940000";
         MySqlCommand command = new MySqlCommand(sql, conn);
         reader = command.ExecuteReader();

Tell me, maybe I'm doing something wrong, or someone, perhaps, faced such a problem?

P.S. In the Unity editor, everything works.