As of HiOS v07.0.06 you can configure hmac-, kex- and encryption algorithms for SSH in the MIB. 

After the software update e.g. from v07.0.05 to v07.0.06 a configuration migration is performed and the default values for these parameters are added. If you do not save the configuration again before rebooting the device you lose these values and no SSH access is possible. 

If this already happened you can set the default values in the MIB. Therefore us a SNMP browser and set the following values:

1.3.6.1.4.1.248.11.25.1.4.19 Hm2SshHmacAlgorithms: d8

1.3.6.1.4.1.248.11.25.1.4.20 Hm2SshKexAlgorithms: de

1.3.6.1.4.1.248.11.25.1.4.21 Hm2SshEncryptionAlgorithms: 94

Make sure that you use the MIB files of v07.0.06 otherwise you won't see these parameters.

And save the configuration afterwards.