Kindly give more details ..like what type of connection you are using or what is your os. If you are on a proxy network try changing the settings in File -> Settings-> HTTP proxy. If that doesn't work look here
AndroidStudio gradle proxy
https://docs.gradle.org/current/userguide/userguide_single.html#sec%3aaccessing_the_web_via_a_proxy
Configuring an HTTP or HTTPS proxy (for downloading dependencies, for example) is done via standard JVM system properties. These properties can be set directly in the build script; for example, setting the HTTP proxy host would be done with System.setProperty('http.proxyHost', 'www.somehost.org'). Alternatively, the properties can be specified in a gradle.properties file, either in the build's root directory or in the Gradle home directory.
Example 12.2. Configuring an HTTP proxy
gradle.properties
systemProp.http.proxyHost=www.somehost.org
systemProp.http.proxyPort=8080
systemProp.http.proxyUser=userid
systemProp.http.proxyPassword=password
systemProp.http.nonProxyHosts=*.nonproxyrepos.com|localhost
There are separate settings for HTTPS.
Example 12.3. Configuring an HTTPS proxy
gradle.properties
systemProp.https.proxyHost=www.somehost.org
systemProp.https.proxyPort=8080
systemProp.https.proxyUser=userid
systemProp.https.proxyPassword=password
systemProp.https.nonProxyHosts=*.nonproxyrepos.com|localhost