Hmm. Hard to say what went wrong. You do not need to set a default coin, this has been deprecated.
Did you follow the instructions at the adapter’s homepage? https://www.dashed-slug.net/bitcoin-altcoin-wallets-wordpress-plugin/coinpayments-adapter-extension/
You mention that you created a wallet and two currencies. But in the case of this special adapter, you should instead just let the cron jobs create the currencies (see step #29). It will create all the currencies that you have enabled in your CoinPayments account, and link them to your wallet. It will also download image logos, set gas management settings, set coingecko IDs which will let the plugin load exchange rate data, and it will set some useful descriptive tags on your currencies. If your site doesn’t have traffic, you’ll need to trigger the following url externally, every minute or so: /wp-cron.php.
If the wallet says it’s connected, the metabox next to it should look like this: 
The currencies that you have connected with the wallet should be listed right below this metabox. Each currency should have 8 decimals (CoinPayments assumes all currencies have 8 decimals), and be linked to your wallet. Do not create the currencies by yourself, just let the cron job do it for you. For example: 
When you list the currencies, if everything is correct, then the hot wallet balance and block height should be shown, like so: 
After checking all of this, you should be good to go. The [wallets_balance] shortcode should be displaying a dropdown with the two currencies.
If you continue to see the “No currencies” message, then please check your browser’s console and let me know if you see any errors.
It’s possible that there is something on your system that’s preventing the WP-REST API from exposing the currencies to the frontend. If you want, I can login to your site and check. (If you want to check yourself, open the network tab in your browser, filter for XHR requests, and reload the page. You should see calls to /wp-json/dswallets/v1/users/1/currencies and responses in json form containing your currencies.)
It’s worth a try to clear your server-side cache, although it’s unlikely that this is the problem. Pages that contain wallet UIs are not cached, because the templates contain dynamically generated JS code.
Thank you for taking the time to field-test the plugin! It sounds like you’re very close to getting it to work. Once you see currencies in the frontend, all shortcodes should work ok. Let me know if you encounter more difficulties.