Make sure to select the correct network. You can switch the network in the settings option within your wallet provider.
Make sure you have enough ETH in your wallet to interact with the platform.You must have ETH in your wallet for the transaction costs -- without it you won't be able to interact. Depending on the network status, the cost of the transactions may vary. At least 0.05 ETH may be required to interact properly.
If you used the Themis protocol in the past and do not find your position in the current markets available, it is possible that you used the Themis V1 protocol. You can find an interface to interact with V1 version of the Themis protocol at https://v1.themis.com/
The following steps may solve your problems:
If you are using Brave browser, switch to another browser to see if the issues are coming from the browser. If it is related to Brave browser, some helpful actions are: clearing cache data and cookies for the site, hard refresh with ctrl + F5 (or cmd + r), disable brave wallet (or the wallet not being used as default, for example MetaMask, Dapper, etc.) or other extensions that might be interfering with proper connection with the wallet. If the site still won't load after taking the steps above, you will have to use the platform in another browser.
Make sure your internet connection is working and stable
Restart the browser and try to connect again
Try to hard refresh the site with control + F5
Check if there are any updates for your browser or wallet provider. If so, update it to the latest version.
In this situation make sure to not keep sending transactions, as every new transaction will be stuck pending until the oldest transaction is confirmed. You can get rid of the stuck transaction by speeding it up or canceling it. Depending on the wallet you are using, you may have that option natively.
For example, MetaMask or Trust Wallet have both the options to cancel or speed up transactions.
Alternatively, if your wallet provider doesn't have this option, you can still drop the stuck transaction by sending a 0 ETH transaction, to your address (to yourself) using the same nonce (number id). You can inspect the nonce in your transaction in Etherscan and use interfaces such as MEW and MyCrypto to send this transaction with a higher gas cost and replace the one that is stuck.