Modpacks showing offline

[MUMBAI_INDIAN]

I have been experiencing issues related to launching my modpacks, they are appearing offline and when I try to install them it pops up with a message saying "the modpack is corrupt and is not available for offline play." even though I am online. can someone please help solve my issue.

 

Error code: 

[B#753] net.technicpack.rest.RestfulAPIException: Error accessing URL [https://solder.mc-complex.com/api/modpack]
[B#753]     at net.technicpack.rest.RestObject.getRestObject(RestObject.java:77)
[B#753]     at net.technicpack.solder.http.HttpSolderApi.getMirrorUrl(HttpSolderApi.java:57)
[B#753]     at net.technicpack.solder.cache.CachedSolderApi.getMirrorUrl(CachedSolderApi.java:134)
[B#753]     at net.technicpack.platform.PlatformPackInfoRepository.getInfoFromPlatformInfo(PlatformPackInfoRepository.java:72)
[B#753]     at net.technicpack.platform.PlatformPackInfoRepository.getPlatformPackInfo(PlatformPackInfoRepository.java:60)
[B#753]     at net.technicpack.platform.PlatformPackInfoRepository.getPackInfo(PlatformPackInfoRepository.java:46)
[B#753]     at net.technicpack.launchercore.modpacks.PackLoadJob$5.run(PackLoadJob.java:180)
[B#753]     at java.lang.Thread.run(Unknown Source)
[B#753] Caused by: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
[B#753]     at sun.security.ssl.Alerts.getSSLException(Unknown Source)
[B#753]     at sun.security.ssl.SSLSocketImpl.fatal(Unknown Source)
[B#753]     at sun.security.ssl.Handshaker.fatalSE(Unknown Source)
[B#753]     at sun.security.ssl.Handshaker.fatalSE(Unknown Source)
[B#753]     at sun.security.ssl.ClientHandshaker.serverCertificate(Unknown Source)
[B#753]     at sun.security.ssl.ClientHandshaker.processMessage(Unknown Source)
[B#753]     at sun.security.ssl.Handshaker.processLoop(Unknown Source)
[B#753]     at sun.security.ssl.Handshaker.process_record(Unknown Source)
[B#753]     at sun.security.ssl.SSLSocketImpl.readRecord(Unknown Source)
[B#753]     at sun.security.ssl.SSLSocketImpl.performInitialHandshake(Unknown Source)
[B#753]     at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
[B#753]     at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
[B#753]     at sun.net.www.protocol.https.HttpsClient.afterConnect(Unknown Source)
[B#753]     at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(Unknown Source)
[B#753]     at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)
[B#753]     at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
[B#753]     at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(Unknown Source)
[B#753]     at net.technicpack.rest.RestObject.getRestObject(RestObject.java:56)
[B#753]     ... 7 more
[B#753] Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
[B#753]     at sun.security.validator.PKIXValidator.doBuild(Unknown Source)
[B#753]     at sun.security.validator.PKIXValidator.engineValidate(Unknown Source)
[B#753]     at sun.security.validator.Validator.validate(Unknown Source)
[B#753]     at sun.security.ssl.X509TrustManagerImpl.validate(Unknown Source)
[B#753]     at sun.security.ssl.X509TrustManagerImpl.checkTrusted(Unknown Source)
[B#753]     at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(Unknown Source)
[B#753]     ... 21 more
[B#753] Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
[B#753]     at sun.security.provider.certpath.SunCertPathBuilder.build(Unknown Source)
[B#753]     at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(Unknown Source)
[B#753]     at java.security.cert.CertPathBuilder.build(Unknown Source)
[B#753]     ... 27 more